Southwest Koi and Pond Association
(SKAPA)

CELEBRATING OUR EIGHTEENTH YEAR! 1996-2014

               

 


Filtration


 


   

KHA Training Program

Filtration Module

By CHRIS NEAVES

AUTHORS SYNOPSIS............................................................................................................. 6

A COMPARATIVE INTRODUCTION.................................................................................... 7

Starting at the Beginning .................................................................................................... 9

DYNAMICS OF A FISH POND............................................................................................ 10

CHAPTER 1: DEFINITIONS................................................................................................. 16

Ambient Ammonia.................................................................................................................16

Ammonia .. 16

Bioconv 16

Chamber... 16

Chemical Filter ...................................................................................................................... 16

Denitrifying Bacteria .......................................................................................................... 16

Filter......... 17

Filters in Parallel................................................................................................................... 17

Filters in Sequence (Series) ............................................................................................. 17

Flow Rate & Specific Flow Rate ....................................................................................... 17

Foam Fractionator................................................................................................................ 17

Heterotrophic Bacteria...................................................................................................... 17

Hydraulic Load....................................................................................................................... 17

Mechanical Filter.................................................................................................................. 18

Media........ 18

Nitrifying Bacteria .............................................................................................................. 18

Organics .. 18

Speed (of water flow)......................................................................................................... 18

Suspended Solids.................................................................................................................. 18

Settled Solids........................................................................................................................ 18

Surface (Flow) Area (of filter chambers).................................................................... 19

Surface Area of Media....................................................................................................... 19.KHA Program – Filtration Module 2

Velocity.... 19

Vegetable Filter.................................................................................................................... 19

UV Lights. 19

Ozone ....... 19

CHAPTER 2: FLOW RATES.................................................................................................. 20

Flow Rate to and from Filters and Bioconverters..................................................... 20

Basic Principles..................................................................................................................... 20

Achieving and Maintaining Flow Rates .......................................................................... 20

Moving Water Around......................................................................................................... 21

Basic Principles.................................................................................................................. 21

Importance of flow rates .............................................................................................. 21

Gravity Fed Pipes: ............................................................................................................ 21

Design Features for Moving Water............................................................................... 22

Bottom Drains...................................................................................................................22

Size of Bottom Drains ................................................................................................... 22

Placement of Bottom Drains ........................................................................................ 22

Pumps....... 22

Pump Capacities................................................................................................................ 22

Power consumption .......................................................................................................... 23

Plac 23

Effects of Frictional Losses on Pump Outputs .......................................................... 23

Claimed water delivery vs. actual water delivery of pumps ............................... 23

Flow Rates Through Bioconverters and Filters.......................................................... 23

Basic Principles..................................................................................................................... 23

Effects of flow rates on ambient ammonia............................................................. 24

Flow Rates and Ambient Ammonia ............................................................................. 24

Low Ambient Ammonia ................................................................................................... 24

Other Advantages of Higher/Faster Flow Rates: .................................................... 25

Dissolving Oxygen into The Water............................................................................ 25

Flow Rates and Removing Solids ..................................................................................... 25

Effects of fast and slow flow rates on mechanical filtration .......................... 26

Pond Turnovers vs. Filter Flow Rates........................................................................ 26

CHAPTER 3: MEDIA............................................................................................................... 27.KHA Program – Filtration Module 3

Definitions ............................................................................................................................. 27

Basic Principles..................................................................................................................... 27

Types of Media ................................................................................................................ 27

The Bioconverter............................................................................................................. 28

Media....... 28

Media Surface Area ....................................................................................................... 29

Hydraulic Loads on Media or Even Flow ................................................................... 30

Physical Lay-out of the Media..................................................................................... 30

Effects on Flow Rate with Different Media in Different Chambers .............. 31

Depth of Filter Media..................................................................................................... 31

CHAPTER 4: FILTRATION.................................................................................................. 32

Basic Principles..................................................................................................................... 32

Mechanical Filters............................................................................................................... 32

Types of Media used in Mechanical Filters................................................................. 33

Open Mechanical Filters ............................................................................................... 33

Closed Mechanical Filters............................................................................................. 33

Settlement Out Side The Pond....................................................................................... 34

Settling Chambers .......................................................................................................... 34

Settling Basins and Discharge Boxes........................................................................ 34

Sand Filters....................................................................................................................... 35

Sand Filter Use Summary:............................................................................................ 36

CHAPTER 5: BIOCONVERTERS......................................................................................... 37

Basic Principles..................................................................................................................... 37

Effects of High Levels of Ammonia .......................................................................... 37

pH and Ammonia............................................................................................................... 38

Bioco 38

Nitrifying Bacteria .............................................................................................................38

Heterotrophic Bacteria..................................................................................................... 39

Starting up Bioconverters ................................................................................................ 39

Seeding Filters.................................................................................................................40

Open Bioconverters (Open media systems) ............................................................ 40

1. Integrated Vortex type........................................................................................ 40

2. Trickle Filters.......................................................................................................... 40.KHA Program – Filtration Module 4

3. Fluidized Bed Filters............................................................................................... 41

7. In Pond Filters .......................................................................................................... 41

Closed bioconverters (close or pressurized systems) .......................................... 41

1. Floating bead bioconverter................................................................................... 41

2. Sinking media bioconverter ................................................................................. 42

3. Combination bioconverters................................................................................... 42

Bioconverter and Filter Size ........................................................................................... 42

Key factors dictating bioconverter size...................................................................... 42

Surface Area – Projected and Total ............................................................................. 43

Projected or Cross-sectional Area of the Individual Chambers ...................... 43

Projected or Cross-sectional Area of the Complete Bioconverter ................. 43

Total Area of the filter material or media............................................................. 43

Effects of different media on flow rates............................................................... 43

Contact Time within the Bioconverter.......................................................................... 44

Shutting Down Filters........................................................................................................ 44

DAMAGING BIOCONVERTERS..................................................................................... 44

CHAPTER 6: MAINTAINING BIOCONVERTERS AND FILTERS.......................... 45

Basic Principles..................................................................................................................... 45

Cleaning Ponds & Filters .................................................................................................... 46

Maintenance ...................................................................................................................... 46

Backwashing Bioconverters and Filters.................................................................... 46

Primary Design Features for Successfully Cleaning Filters .............................. 46

Cleaning and Damage ...................................................................................................... 47

How Often Should Filters be Cleaned?.................................................................... 47

Water Changes (water changes out) ............................................................................. 47

Fresh Water Caution.......................................................................................................... 48

CHAPTER 7: ALTERNATIVE METHODS OF FILTRATION AND

BIOCONVERSION.................................................................................................................. 49

Ion Exchange - Zeolite.................................................................................................. 49

Activated carbon............................................................................................................. 49

Water Changes (water changes out) ......................................................................... 50

UV Lights ........................................................................................................................... 50

Vegetable (plant) Filters............................................................................................... 50.KHA Program – Filtration Module 5

Streams as Filters .......................................................................................................... 50

Foam Fractionation .......................................................................................................... 51

CHAPTER 8: EFFECTS OF CHEMICALS & MEDICATIONS ON FILTERS.......... 52

Effects of Various Chemicals and Medications on Filters ................................. 52

CHAPTER 9: DEVELOPING AN EYE FOR PROBLEMS ASSOCIATED WITH

FILTRATION ........................................................................................................................... 53

Message to Koi Health Advisors. .................................................................................... 53

Case #1 ... 54

History 54

The Problem...................................................................................................................... 54

Questions - Case #1 ....................................................................................................... 54

Analysis & Solutions ....................................................................................................... 54

Case #2 .. 54

History 54

The Problem – Case # 2 ................................................................................................ 55

Questions - Case # 2..................................................................................................... 55

Analysis & Solutions – Case # 2.................................................................................. 55

INDEX......... 56.KHA Program – Filtration Module 6

AUTHORS SYNOPSIS

This KHA training module must be read in conjunction with the AKCA

Guide to Filters and pre-filters and with the KHA sections on Pond

Design and the section on Water Quality.

Whilst "filtration" on koi ponds has become a somewhat controversial

subject full of emotion, there are basic principles that apply to all

variations hobbyists may encounter.

In this section, the terms ‘filters’ and ‘bioconverters’ will be used to

describe the devices that remove solids and chemicals, respectively,

from pond water. More complete definitions will be given later.

As a wide variety of filters and bioconverters are available to the

hobbyist. Koi Health Advisors must look past advertising claims, past

personal points of view and past complexity.

It is a fact that all filters and bioconverters work. The human element

transgresses certain natural laws of limitations and the failure of the

system results.

A bioconverter is not working and will not work in only two

circumstances. 1) when it is new and 2) when it has been damaged or

destroyed by chemical or medication treatments to the pond or a lack

of oxygen. In all other circumstances the bioconverter is working to

some degree or the other.

Bioconversion is a simple and natural process in nature. Nature "works" –

it’s as simple as that. The number of living organisms that can be

successfully accommodated in a limited volume of water (the pond) is

determined by the amount of oxygen removed from the water and the

amount of toxic waste products added to the water during the process

of metabolism by all living organisms in the pond.

Our ponds are a limited volume of water. In order to successfully

sustain, in a healthy condition, a large number of koi, we have to re-cycle

the same water. The re-cycled water is re-conditioned by removing the

unwanted substances such as carbon dioxide, solids and nitrogen waste

products then adding in vital oxygen. This purified and rejuvenated

water is returned to the pond as quickly as possible for the benefit of

the fish and the bioconverter.

It is remarkable that all bioconverters and filters work. The filter

system simply has to remove the excretion in the water faster than it is

added. The filter must also remove organics such as algae faster than

they are produced in the pond. We simply have to add oxygen at a

faster rate than it is removed. The purified water must return to the.KHA Program – Filtration Module 7

pond as fast as possible.

The Koi Health Advisor Filtration module/section does not promote a

specific bioconverter or filter design idea. All filter concepts are

discussed.

This Module is viewed as a dynamic lecture. New facts and ideas are

continually emerging. As this information becomes available it will be

incorporated into this module.

A perfect pond can be described as one in which the fish are alive and

healthy for some time, the pond is truly clear and the pond does not

leak. The rest is robust debate at the edge of the pond on how to

achieve this.

Chris Neaves

CONTINUUM – Koi Ponds are remarkably similar to the human

body – we compare these similarities in - The Comparative

Introduction …………………..

A COMPARATIVE INTRODUCTION

The simplicity of filtration on a koi pond is remarkable. The pond, the

piping, the filtration, the bioconverter and the returning water to the

pond can be compared to the human body.

Our lungs introduce air into our systems and cells by making gaseous

exchange possible. The oxygen allows chemical processes to occur in the

cells. This activates our bodies. The liver is a filter removing toxins and

impurities from the blood. The kidneys, colon and skin excrete harmful

by-products to waste.

There is one golden thread that enables all the functions to work –

circulation of fluids within the body. These fluids carry a host of vital

substances from oxygen to white and red blood cells to hormones to

carbon dioxide etc.

No matter how large and strong the heart is (or a pump on a pond) it is

useless unless piping, in the form of veins and arteries, are free of.KHA Program – Filtration Module 8

restrictions and open for the circulation of blood. The blood that

carries nutrition and oxygen into the cells also carries waste products

away. Within the blood, a host of cells circulate to assist with the

immune system, the nutrition and the oxygenation of the body cells.

It is an effective circulation that ensures the success of the organism.

A failure of any one of several organs will result in the death of the

organism. For example, liver failure will result in the body being unable

to filter and remove impurities from the bloodstream. The body will

then die. With kidney or bowel failure the same thing - impurities in the

body will reach toxic levels within a remarkably short time and the

organism will die. A healthy circulation system with strong heart, open

veins, open arteries, is the key to health within the body. The same

principles apply to our ponds.

The human body is approximately 70 - 80% water. Our ponds are water

and fish are 80% water. The volume of water of the pond is the living

environment of our fish. The pond water is piped (analogous to the blood

vessels) to a pump (the heart) and through various filters (equated to

the liver, kidneys etc. of the body) for purification and rejuvenation.

The pond water is brought into contact with the atmosphere via

waterfalls, streams, and/or venturis for gaseous exchange to take place

– exactly like the lungs. Oxygen is dissolved into the water and unwanted

gasses pass out of the water just like the lungs.

Failure of any one of these systems will result in the death of the pond.

When the pond dies the fish will die.

The purpose of any filtration on a koi pond is to remove unwanted

substances from the water – continuously and quickly.

Just as removing the sugar and the tea leaves from a cup of tea would

need two different approaches, so too in a koi pond different

approaches for different problems are needed.

Impurities that are dissolved in the water need chemical removal by

bacteria (bioconversion) or with charcoal or zeolite. Impurities in the

form of solids need mechanical removal.

A bioconverter is a remarkably simple concept. This involves providing

enough space for naturally occurring bacteria to grow on. These

beneficial bacteria do a vital job in nature and in the pond of chemically

changing toxic fish waste to less toxic substances. It’s as easy as that.

Fascinatingly the bioconverter is not only home to nitrifying bacteria

but home to countless other varieties, many of which have not been

identified yet. This incredible diversity of microscopic bacterial life

plays a vital role in the success of your pond.

Piping that is clogged or piping that is too small or even piping with

numerous bends will restrict and reduce the flow rate, no matter how.KHA Program – Filtration Module 9

large the pump. These losses can be substantial to the point of

compromising the design of the system.

Losses caused by restrictions in unhealthy veins and arteries in the body

compromise the circulation and the health of the person. Exactly the

same occurs in a pond.

Starting at the Beginning

Viewing the entire pond system with the piping, the pumps, the various

aspects of the filter and the returns it is literally a circle. Where do we

begin within the circle? After all, a circle has no starting point and no

end. As water is the medium in which fish live we will begin with the

water.

Before the fish can be introduced into a pond, before bacterial growth

will occur, before there will be any life in the water it has to be

activated. Nature activates water or the atmosphere for that matter,

with a gas - oxygen. We therefore, have to introduce oxygen into the

system as the starting point. Once oxygen is introduced into the water

it must be circulated throughout every part of the system. Just as in

the body, the oxygen in the blood supply is circulated to every cell and

every organ. Should the oxygen supply be cut off from any part of the

body for long enough, that area will die.

In order to introduce oxygen into the bloodstream or into the pond

water, the water must flow - it must move. Once the water begins to

move and there is a flow through the system, oxygen will be introduced

into the water with the natural gas exchange of the atmosphere and the

system will become active and live. The fish can then be introduced into

the system. Once the fish are introduced they will be fed and once they

feed, impurities will be excreted into the water. The combination of

oxygen and excretion from the fish results in the growth of naturally

occurring nitrifying bacteria. These bacteria will grow on all surfaces

within the pond. There they begin their job of converting the fish

impurities to less toxic substances. Bacteria take time to reach large

enough numbers to convert all the ammonia to nitrite and, at a later

stage, to nitrate.

It is as easy as that.

Ponds generate an enormous amount of pollution or unwanted material.

This enters the pond system in various forms. Algae accounts for much

of the organic build up in a pond. Various other substances such as dust,

debris, etc contribute to the build-up of unwanted substances in the

pond

This organic matter ends up in the filter system and must be removed

regularly to ensure a healthy environment. The maintenance of a pond.KHA Program – Filtration Module 10

system is absolutely critical to the long-term health of the fish.

You would not consider trapping ten dogs in a closed courtyard and

never ever cleaning it. The pollution these dogs would create in a short

time would result in illness, stress and death. Exactly the same applies

to fish in the pond.

If you, as Koi Health Advisors, understand the principles and look at the

concept of ponds as a global concept, you will have much less difficulty

in analysing problems that occur within systems.

CONTINUUM – Fish ponds are not static environments therefore,

the dynamics of a fish pond are discussed next in – The Dynamics

of a Fish Pond …………………..

DYNAMICS OF A FISH POND

Water is a very remarkable substance. The extraordinary properties of

water have a direct bearing and influence on the daily existence of our

fish. A fish’s body is composed of more or less 80% water. So it is easy

to envisage fish as a volume of water separated from a volume of water

(the pond) by a thin membrane (the skin). The most insignificant changes

in the pond environment will therefore, have a direct and almost

instantaneous influence on the life of our fish.

Each and every one of these Influencing Factors, let’s call them "Ifs," is

dynamic. This is very important to remember when dealing with pond

situations. Sometimes we can create problems that are not really there

by viewing various parameters in isolation. During the course of a 24

hour day each IF (Influencing Factor) has a natural dynamic change.

These dynamic variations can be recorded and a daily pulse or oscillation

can be observed. As the seasons change so do some of the parameters -

the most obvious is temperature. A pond or water system has a natural

bio-rhythm of life to which fish have adapted to during the course of

their evolution.

At any point of time, during the day or year, a measurement of one or

the other IF will possibly be different when compared to another

measurement taken at a different time of the day or year. These

fluctuations or dynamics should never be viewed in isolation. A single

reading on a test kit will present only an incomplete view of what is.KHA Program – Filtration Module 11

actually going on in your pond. Therefore, you may be panicking and

trying to make adjustments for nothing.

Nitrifying Bacteria

The nitrifying bacteria found in the places we encourage them to grow

i.e. the bioconverters or any wet surface in our koi ponds, move through

a dynamic range of abilities.

As they grow in the bioconverters and on all the parts of the pond they

become stronger. Their collective ability to convert ammonia to nitrite

then nitrate increases as their populations increase, fuelled by an

adequate food source and a good supply of oxygen.

As temperatures drop in the winter months (below about 50ΊF / 10ΊC),

these bacteria do not die off but become dormant. In periods when

their food supply is reduced they also become dormant. When koi

populations are increased and / or the feed to the existing fish

population is increased, the ammonia in the water increases and the

bacteria population will increase provided sufficient surface area

(usually in the bioconverter) is available.

As these factors vary, so do the nitrifying bacteria populations. The

nitrifying bacteria are dynamic and ever adapting in the pond situation.

pH

In the morning, the pH will be low compared to a test done in the late

afternoon. The buffering capacity of the water will play a major role in

the fluctuation of pH during the course of a day. The pH you record may

be unique to your pond. Don't be influenced by "perfect situations". It

may be slightly alkaline with a pH of around 7.8 - 8.2. It may be that

your particular pond has a pH range of 7.2 - 7.6. Or there may even be

greater fluctuations. This is the natural, daily, pH cycle of your pond. I

strongly advise against attempting to adjust the pH to a perceived

perfect figure of say 7.2.

Measuring the pH in the late afternoon you will inevitably find it is on

the high (alkaline) side. The addition of acid to pond water to lower the

"high" pH can be disastrous at this point in time. The acid will lower the

pH and so will the natural pond cycle during the night. The result could

be - a pH crash.

Sudden substantial fluctuations in pH values will stress koi and possibly

kill them. Fish do not tolerate sudden substantial changes in water

quality very well. If they do not die, then the stress they suffer may

become a contributing factor to lowered resistance and a possible

disease infection. Measuring pH should be done in conjunction with

measuring total alkalinity. The total alkalinity will give you an indication

as to the buffering capacity of the water against pH variations.

The amount of algae (mostly free floating, single cell algae that makes.KHA Program – Filtration Module 12

the pond water green) can have a dramatic effect on pH, pushing the pH

to very high levels in the evening after a full day’s photosynthesis. The

opposite effect is observed by a lowering of the pH in the early

morning.

Not only the koi but also the toxicity of ammonia as well as the bacteria

in the filter are affected by pH. Should your water pH fluctuate

through a narrow range, your water is well buffered. Should there be

large fluctuations you may need to buffer the water a little. The pH

should not rise much above 8.5 at its maximum reading.

Koi have adapted to survive in a pH range of 6.5 - 9. Providing the

fluctuation within this pH range in not large and providing the pH change

is not sudden.

Temperature

On most occasions temperature will be lowest in the morning just before

sunrise and the highest at sunset. (Unless your pond is built on a nuclear

waste dump, which generates its own heat). Temperature is influenced

by the amount of sun, the intensity of the sun the pond receives and

other factors such as the wind speed during the day or night.

Evaporation cools the water. Generally speaking koi should not be

subject to more than about a 5ΊC (9ΊF) sudden change in water

temperature. Always adjust the temperature gradually when moving koi

around. An upward movement is tolerated better than a downward

movement in temperature. Most ponds have a 1Ί - 3ΊC (1.8Ί - 5.4Ί F)

variation in temperature in a 24 hour day / night cycle. Koi are more

affected by temperature variations at lower water temperatures. And

you will notice koi are more affected by a sudden lowering of water

temperature than a sudden raising of water temperature.

Certain areas in the country can experience a 10 - 15ΊC (18Ί - 27Ί F)

atmospheric drop in temperature in a day accompanied by high winds.

Ponds can and do drop temperature significantly in these circumstances.

The koi suffer from stress and disease problems can occur later.

The koi can be helped through large, sudden water temperature changes

by the addition of a good grade course salt at a rate of 1 - 2 kg per

1000 litres (or about .85 – 1.7 lbs per 100 gallons) immediately after the

temperature has dropped.

Oxygen

Oxygen is possibly the single most important element in pond water -

and a most neglected aspect of koi keeping. For life to exist in water

there must be oxygen dissolved in it. The fish, the bio-filter, organic

decomposition etc. all extract oxygen from the system. Oxygen is

introduced into the water through gaseous exchange between the

atmosphere and water molecules. Oxygen is introduced into the pond via.KHA Program – Filtration Module 13

contact with the atmosphere through design considerations such as

streams, waterfalls and apparatuses such as venturis and air blowers.

High turnover rates will promote higher oxygen levels. Photosynthesis

by algae during the day introduces additional oxygen, but removes it at

night. Air under pressure through venturis can cause gas imbalances in

the water and need careful consideration in their placement in the pond.

Oxygen levels can fluctuate dramatically during the day and night as

well as during periods of high and low temperature. There can be

significant oxygen variations in ponds with poor circulation or in ponds

which do not move the water away from the bottom of the pond. i.e. the

point furthermost from the atmosphere. There is less oxygen in pond

water at higher altitudes (6000 ft above sea level) - about 18 - 20% less

than at the coast. There is continual competition in the pond for the

limited amount of oxygen available at any given time. The fish, the

plants, the micro organisms all need oxygen rich water - all the time.

Algae and submerged plants have a dramatic influence on oxygen levels

in a pond during a 24 hour day / night cycle. The photosynthesis process

during sunlight may rocket oxygen levels to saturation point and beyond.

However, a dramatic plunge in oxygen with the reversal of the

photosynthesis process at night can spell disaster, even to the point of

fish suffocating in ponds at dawn.

It has been found that if the oxygen levels are 25% below optimum

levels first thing in the morning, growth rates are reduced. The turn-over

rate will have a direct bearing on oxygen levels as will the stocking

densities of fish. The faster the turnover rate the more water will come

into contact with the atmosphere and the more gaseous exchange will

take place. The more fish in the pond, the less oxygen in the water, as

they are all respiring all the time.

Higher temperatures in summer mean there is less oxygen that can be

dissolved into the water. Higher temperatures result in faster

metabolism, which in turn means that the less-available oxygen is

extracted faster at the same time it is needed in greater quantities by

the fish and other life forms.

A shortage of oxygen will be noticed by observing the koi collection

first thing in the morning. If the koi are moving lethargically and

hovering near the surface you may well have an oxygen deficiency.

Oxygen shortages have been measured in ponds with fancy pumps and

filters - but with a lack of exposing the water molecules to the

atmosphere. A shortage of oxygen can also be observed by watching the

respiration of the fish. If the fish are respiring heavily or "piping" they

could be, 1. stressed, 2. have a gill problem, 3. the pond water could be

low in oxygen or 4. the fish could be exhausted for some reason. (and

what have you been doing during the night to exhaust yourself, my little

Cynthia Sanke?).KHA Program – Filtration Module 14

Ammonia

The levels of ammonia and toxicity of ammonia are never constant. A

few hours after feeding the ammonia level will rise as the nitrogen

wastes of the fish are excreted. This can actually be measured. A

measurement just before feeding should produce the lowest or no

ammonia reading (if everything is working). However, an hour or two

after feeding a high ammonia level will be recorded as the fish are now

excreting their metabolic waste products. Interestingly, a

corresponding drop in oxygen levels at this time has also been measured

in ponds as the koi consume more oxygen for the metabolism of the

food.

The higher the temperature the faster the metabolic rate and the

quicker ammonia will be released into the surrounding water. However,

there is another dynamic related to ammonia - the toxicity of ammonia

(NH3) is not constant during the course of a single day. Ammonia is

found in two forms in the pond. The toxicity of ammonia is pH

dependant. Ammonia changes from ammonia to ammonium (NH4 + ) as pH

drops i.e. it becomes less toxic. As pH rises (naturally during the day)

the ammonium (or a percentage of ammonia) converts back to toxic

ammonia.

Whilst very high pH above 9 makes a higher percentage of ammonia

more toxic and has certain negative effects on koi, low pH has other

effects on the pond system. The bacteria in the filter are oxygen and

pH dependent. The bacteria that inhabit the filter medium are affected

by pH. The nitrifying bacteria that oxidise ammonia to nitrite have a

optimum pH range of 7.8 - 8.5. The lower limit for reasonable growth

for nitrifying bacteria is given as pH 7.0 - 7.6. While the upper limit is

9.4. Around pH 6.5 nitrifying bacteria cease to function.

So what now?

Into this dynamic pond system we introduce two critical factors - fish

and man. How can our koi possibly survive in an environment that can

become 100 - 200 times more alkaline / acidic, have a temperature

change of more than 40ΊF (5....C), have oxygen levels that can drop and

rise dramatically, and have a shifting ammonia / ammonium percentage in

a single day? How can our fish possibly survive the bombardment of

toxic chemicals that are added to the pond in the name of medications?

The average enthusiast does not have the money to spend on equipment

to monitor the water continuously. How can he possibly monitor all these

IF's (Influencing Factors) continuously, make daily adjustments, provide

the perfect environment for his koi?

The answer is simple - if your koi are alive and healthy and growing well -.KHA Program – Filtration Module 15

you are doing it right. Your koi are the best test kits you have. It may

be a joke amongst koi collectors that when a new pond is built they

always suggest placing a few "testers" into the new pond to "test" the

water. A joke yes - but it is an excellent way of testing the water for

your new arrivals and new pond system.

The ancestors of Koi, the common carp, have been living successfully in

freshwater rivers for millions of years. There are ancient fossilised

remains of the ancestors of carp. It is a scientific fact that whilst a pH

of 7 - 7.5 is advocated as "ideal" for keeping koi. Koi will live

comfortably in a pH range of 6.5 - 8.5. A temperature range of 22....C -

28....C (72....F to 82....F) is ideal for keeping koi. However, they winter well

down to 10....C (50....F). And provided the temperature is not below 8....C

(46....F) for too long a period of time, they suffer no adverse affects

after winter. Some reports give the lower temperature limit for winter

survival as 35ΊF. The critical factor is these fluctuations must be

gradual. Actually the less the fluctuations or the more gradual the

temperature fluctuations, the less stressful the environment.

Oxygen levels are maintained by circulating the water correctly in the

pond and by bringing the water into contact with the atmosphere

continuously. The faster the turn-over rate of the whole system, the

better.

Ammonia levels can be controlled successfully by providing additional

surface area for bacterial growth. This extra surface area is often

referred to as the bio-filter or bioconverter. The high oxygen levels

provided by high turn-over rates will activate the bacteria and the

metabolism of the fish.

The natural immune systems and osmo-regulation of the fish’s body is

adapted over millions of years to counteract natural fluctuations in the

water and attacks from the outside world. Provided the fluctuations are

not too great or too sudden the fish has the ability to adjust and

survive the daily, monthly and annual bio-rhythms of the pond.

CONTINUUM – In order to discuss filtration we must define

what we are talking about – Chapter 1: Definitions …………………..KHA Program – Filtration Module 16

CHAPTER 1: DEFINITIONS

- as they relate to koi pond filtration

Ambient Ammonia

Ambient ammonia is the background level of ammonia in the pond water

and will likely vary over the course of a day. [There can never be zero

ammonia in the pond as the koi are excreting ammonia in the pond whilst

the bioconverter is removing ammonia from the water]

Ammonia

Dissolved gas excretion of fish primarily through the gills, as a result of

the metabolism of the body ammonotelic which means they discharge up

to 70%of their nitrogenous waste via the gill lamellae.

Bioconverter

A bioconverter is a specialized or dedicated area of the pond system

designed to provide the proper environment for large colonies of

beneficial bacterial to grow. The nitrifying group of bacteria, the

chemolithotrophs, as well as the organic consuming bacteria, the

heterotrophs, grow in the bio-converter. In some literature these areas

are referred to as biological filters or biofilters.

Chamber

An area or enclosure where media is housed or settlement takes place.

Chemical Filter

Zeolite and Activated Carbon are substances (or perhaps geological

materials) that absorb and adsorb ammonia and other substances

directly from the pond water.

Denitrifying Bacteria

Free-living bacteria that convert nitrates to gaseous nitrogen and

nitrous oxide. These are anaerobic bacteria and their cellular

respiration occurs in the absence of oxygen..KHA Program – Filtration Module 17

Filter

A physical process (i.e. one not reliant on chemicals or biological

organisms) to remove solid particles from the water.

Filters in Parallel

When the water to the filter chambers is divided into two or more

portions and each portion travels through only one of the filter

chambers, the filter chambers are said to be in parallel.

Filters in Sequence (Series)

When the water moves from the first chamber or container to the

second chamber to the third chamber etc., the filters are in sequence

or series.

Flow Rate & Specific Flow Rate

Flow rate is the volume of water that flows past a given plane (or

through a filter chamber of a given surface area) over a given length of

time. Expressed in terms of volume/time. (e.g. Gallons Per Minute GPM).

Specific flow rate: the flow rate divided by the projected area across

which the flow takes place and is given in: volume/time/area. If the

specific length units of volume and area are the same, e.g., feet as in

cubic feet and square feet, it can be an expression of velocity, but only

if no media is involved (water only).

Foam Fractionator

Also termed foam floatation and protein skimming, this process removes

organic matter (DOC) and fine solids from water.

A narrow device with a rising column of air bubbles and a descending

volume of water. Used to remove DOC (dissolved organic carbon or

scum) from the pond water.

Heterotrophic Bacteria

A species of bacteria that digest (intake) organic material to obtain

their energy.

Hydraulic Load

The relationship of flow rate to the available media surface area - is

called the hydraulic load on the media bed. The first objective of

hydraulic load is to encourage the water to move through the filter bed

evenly at all points of contact between the media and the water..KHA Program – Filtration Module 18

Mechanical Filter

Mechanical Filters will be referred to as filters. These are areas where

suspended and settled solids are collected for removal from the pond

system.

Media

Any substrate, which is used to either support living organisms (e.g.

bioconversion) and / or any substrate to filter material from the water.

Nitrifying Bacteria

Bacterial species found in nature that oxidise ammonia to nitrite and

then nitrate. These are chemolithotroph species of bacteria that live in

an oxygen rich environment, utilize mostly inorganic (without carbon)

compounds as their energy source, and require carbon dioxide (CO 2 ) for

their source of carbon.

Organics

Used to refer to any material that consists of live or dead cells, or

carbon containing material that is capable of being broken down by

biological means. A material containing carbon that is derived from a life

form. Examples – algae, leaves, fish faeces.

Speed (of water flow)

See velocity

Suspended Solids

Suspended solids are the non-dissolved pollutants that remain

suspended in the pond water. Examples of suspended solids are fine

dust, pollen, dead algae and all fine solids and/or those solids near zero

buoyancy.

Settled Solids

Settled solids are the non-dissolved pollutants that settle towards the

bottom of whatever reservoir they are in. Examples of settled solids

are heavier particles of dust, water logged organic material and leaves.

One of the prime pollutants, in terms of quantity, in pond water is dead

algae. This accounts for as much as 60 – 70% of the organic material.

However, in some lightly loaded ponds, it may be 90% of the organic

material which clogs up the filter system..KHA Program – Filtration Module 19

Surface (Flow) Area (of filter chambers)

Cross-sectional area or Projected area (the area that would appear if

you took a picture and projected it onto a screen) - this term is

sometimes used in engineering.

The projected surface area of the media at right angles to the flow of

water in the individual chamber(s) in the filter or bioconverter.

Different from the surface area of the media.

Surface Area of Media

The total surface area of the media in the bioconverter and can vary

greatly according to the type of material. Surface area of media relates

to the area on which the bacteria may grow.

Velocity

The speed at which a fluid travels. In our case the speed at which the

pond water travels through any part of the system.

The velocity or speed of the water is less in a bigger tank (given the

same flow rate through the tank).

Vegetable Filter

An area in the pond system, usually away from the koi, where plants are

encouraged to grow. The pond water is run through and over the plants

and/or the plants’ roots in this area (such as a stream bed).

UV Lights

Ultra-Violet Lights are a type of light that has a specific band of

wavelengths primarily used for controlling algae. Now referred to as

Ultra-Violet sterilizers by many in the hobby.

Ozone

Tri-atomic form of oxygen.

CONTINUUM – The pond must be activated before life can exist

and live in the water – we must move the water – Chapter 2: Flow

Rates …………………...KHA Program – Filtration Module 20

CHAPTER 2: FLOW RATES

Flow Rate to and from Filters and Bioconverters

Flow rate is critical for all intensive aquaculture systems, as it

determines the rate at which oxygen and other resources (e.g. calcium

carbonate which will buffer a system’s pH) are brought into the system,

and also the rate at which excretory products such as faeces, carbon

dioxide and ammonia are removed from the system.

Stocking densities and flow rates are intimately connected. In general,

the higher the stocking density the faster the turnover rate should be.

Basic Principles

1. All the water should pass through the filter system. Any water

by-passing the filter will dilute the effect and efficiency of the

filter system.

2. The entire pond volume should pass through the filter system as

quickly as is practical and returned to the fish, i.e. the turn-over

rate of the pond volume should be high.

3. Once in the mechanical or settlement part of the filter, the

water should slow down. Slow moving water encourages

settlement. Flow rates of the entire system must be maintained.

Increasing or decreasing the size of the filter chambers can

adjust the slowing down or speeding up of the water flow in the

filter system.

4. In the bioconverter part of the system, the water can flow fairly

quickly as the conversion of ammonia to nitrite to nitrate takes

place immediately on contact with the nitrifying bacteria. The

flow rate must not be too quick or the water may flush the

heterotrophic bacteria from the media.

Achieving and Maintaining Flow Rates

Basic Principles:

1. The heart of the system – the pump, activates flow rates.

2. It is critical that the pump run 24 hours a day..KHA Program – Filtration Module 21

3. Generally speaking the larger the pump the greater the flow

rate.

4. Larger pumps cost more to run.

5. Different types of pumps will have different running costs as the

pumps have electrical consumptions.

Moving Water Around

Basic Principles

1. Water is usually moved around the system and between various

discrete sections of the system through piping.

2. Piping on a koi pond can be equated to the veins and arteries in

the body.

3. Restricted piping will negatively affect flow rates and water

delivery.

4. Various design features are used on ponds to collect the water

and direct it in a specific direction.

Importance of flow rates

1. The pond water has to be moved from the pond to the

bioconverter and the mechanical filter.

2. Bioconverters and filters can be some distance from the pond or

they can be at the pond’s edge. Some old-style designs are even

IN the pond. The design considerations will dictate the

placement.

3. The size and length of the pipe work in combination with the

pump will dictate the flow rate irrespective of the size of the

filters and bioconverters. Pipe work will alter the flow rate

calculations because of frictional losses. Additions with

restrictions, such as sand filters and venturis, will greatly reduce

the flow rates.

4. In general, the faster the turnover rate of the whole system,

the faster the impurities will be removed and the more oxygen

will be dissolved into the water.

5. The faster the impurities such as ammonia are removed, the

healthier the pond water will be. The faster the organic matter

such as algae is removed the clearer the water will be.

Gravity Fed Pipes:

In order to maintain correct high rates throughout the entire system,

an important point to consider is that far more water is pumped through.KHA Program – Filtration Module 22

a given pipe under pressure than can be fed through the same pipe

under gravity.

See KHA – Pond Design section by Burt Ballou

Design Features for Moving Water

Bottom Drains

A bottom drain is, as the name implies, an outlet or drain located usually

at the lowest point in the pond or filter. These drains provide several

functions: 1) to remove the heavy debris from the pond or filter, 2) to

remove the bottom water (usually the least oxygenated water in the

pond) 3) to provide circulation of the pond water by drawing the top and

best oxygenated water toward the bottom.

In a pond, the bottom drains can feed water directly to the pump, they

can feed water to a discharge box or settling chamber or they can be

used to flush the bottom water directly to waste. In filter chambers

they are used to flush the accumulated solids to waste.

Size of Bottom Drains

See KHA – Pond Design Section by Burt Ballou

Placement of Bottom Drains

The placement of bottom drains can have an effect on the circulation of

the pond water and the efficient removal of impurities from the water.

For example, placing a bottom drain directly beneath a waterfall will

result in purified water being drawn directly out of the pond instead of

circulated and diluted around the pond.

If there is circulation the entire pond will have a vortex type action and

settlement will take place in the centre of the pond. Placing the bottom

drains together in the centre of the pond would result in the solids

being drawn from the area where they settle.

See: Pond Construction Section for examples of bottom drain layouts

Pumps

Pumps are the heart of the pond. The heart pumps blood to each cell.

The pump on a koi pond must pump the water from the pond, through

the filtration system and return it to the pond.

Pump Capacities

See KHA – Pond Design section by Burt Ballou.KHA Program – Filtration Module 23

Power consumption

See KHA – Pond Design section by Burt Ballou

Placement

See KHA – Pond Design section by Burt Ballou

Effects of Frictional Losses on Pump Outputs

No matter how powerful the pump, the final output will be restricted by

several factors. Restrictions will reduce flow rates and ultimately

affect the stocking density allowable in the pond.

Smaller diameter piping will reduce the flow. Longer lengths of piping

will reduce the flow. Bends and elbows reduce the flow.

Using larger diameter piping will improve the flow rates.

Reducing the number of 90Ί bends will improve flow rate. A single 90Ί

bend has the equivalent frictional loss of about 50ft of piping.

Claimed water delivery vs. actual water delivery of pumps

There is often a disparity between claimed flow rates and actual

delivery of water of pumps. Different makes of pumps may have the

same power motor driving them but often they deliver different

amounts of water.

Flow Rates Through Bioconverters and Filters

Basic Principles

Oxygen must be introduced into the pond water before the fish can be

introduced and before nitrifying bacteria will develop.

Water passing through the bioconverter chamber and media should not

be so fast that conversion of impurities is minimal. Very fast flow rates

through bioconverters can scrub off the bacteria growing on the media.

Conversely the flow rate should not be so slow that water that has been

purified is sitting in the filter chamber taking up space that could be

used more efficiently. It is remarkable that both fast and slow moving

flow rates work to a degree. However, filters that flow too fast and

filters that flow too slowly are inefficient.

Mature filters with large masses of nitrifying bacteria will be able to

convert almost all ammonia to nitrite and nitrite to nitrate on a single

pass through the filter medium. This should be the goal - small, cheap to

run, easy to maintain and efficient.

The turnover rate of the whole pond should be as fast as possible, but.KHA Program – Filtration Module 24

the flow rate through the filter/bioconverter system should be set so

the solids can be removed and efficient nitrification can take place.

Effects of flow rates on ambient ammonia

The flow rate of the pond water through the filter chamber or

chambers has a bearing on the levels of oxygen and ammonia in the

system. This is a very important consideration because it directly

effects the ambient or daily background ammonia levels as well as

oxygen levels in your pond.

The fact is, the actual ammonia level in a fully recirculating pond can

never be zero - even if the filter design is so efficient in design as to

remove 100% of the ammonia, nitrites and nitrates that passes through

it.

There will always be some quantity of ammonia in the pond water by

virtue of the fact that the fish are continuously adding ammonia to the

water. The filter can only remove ammonia from that portion of the

pond water that is moving through it at any given time. However as one

portion of the pond water has ammonia removed, the fish in the pond

are polluting the balance.

The greater the fish load, the higher the ambient ammonia level will be

(background ammonia). The filter design should also take this into

account. The bioconverter should be designed in such a way that the

water that is purified is returned as quickly to the pond as is practical.

From this explanation, it should be obvious that the greater the number

of pond volumes moved through the filter each day, the lower the

ambient (average daily background) ammonia level will be.

Flow Rates and Ambient Ammonia

Pond volume, bioconverter volume and flow rates are intimately

connected.

In a properly designed system, the ambient ammonia level, while never

actually zero, it is simply too low to be measured with most hobbyist

test kits.

Low Ambient Ammonia

In order to ensure an acceptably low ambient ammonia level, the filter

should be designed to process at least 12 pond turnovers per day. Thus,

one-half of the pond's volume will be pumped through the bioconverter

every hour. Increasing the turnover rate to one full pond volume per

hour (24 turnovers per day) would be even better. However, a close

examination of the costs for the larger pump and higher electricity

running costs should be made..KHA Program – Filtration Module 25

To determine a rate of one-half pond turnover per hour, divide the

volume of the entire system, the pond, the filter and the bioconverters

volume by two. This will give you the flow rate entering and exiting the

filter in gallons or litres per hour.

For example if a pond has a total capacity of 5000 gallons (19,000

litres), then at one-half turn over per hour we would need a pump that

would be capable of pumping a minimum of 2500 gallons (9,500 litres)

per hour, or 42 gallons (160 litres) per minute.

This would be the water actually delivered after various restrictions are

taken into account.

Other Advantages of Higher/Faster Flow Rates:

1. It is an undisputed fact that koi have better growth, live longer

and their colours are brighter and more intense in oxygen rich

environments.

2. It is also and undisputed fact that biological filtration is more

efficient and flourishes in a more oxygen rich environment.

3. Therefore, your pond system should include a method of aerating

the water at ALL times to replace the lost oxygen. In other

words, the pump must run continuously and provide a high

turnover rate.

Dissolving Oxygen into The Water

The only way oxygen can dissolve in water is by contacting the water.

This is typically accomplished by diffusion between molecules of water

in contact with the oxygen in the atmosphere.

Some interesting deductions can be made from this fact. a. all the

water's molecules should be brought into contact with the atmosphere

at some time during a complete circulation cycle b. the water should

ideally be brought into contact with the atmosphere as much as possible

(surface area and turnover rates) to assist with the diffusion of oxygen

into the water and the release of unwanted gasses into the atmosphere.

If the water was drawn exclusively from the surface of the pond and

returned to its surface, the oxygen levels in the lower levels of the pond

water may become critically low (unless supplemental circulation within

the pond is provided like air stones). The water will take on a "dead"

look. Anaerobic bacteria will flourish on the floor. The settled solids will

decompose and produce the deadly Hydrogen Sulphide, gradually

poisoning the system and fish.

Flow Rates and Removing Solids

Higher turnover rates through filters will remove solids at a faster.KHA Program – Filtration Module 26

rate. In many cases this is the difference between murky water and

clear water. However, if the water moves too fast in the settlement

chamber nothing settles out.

If the turnover rate is faster or equals that of the production and

accumulation of solids, then the water will clear.

Effects of fast and slow flow rates on mechanical filtration

See mechanical filtration

Pond Turnovers vs. Filter Flow Rates

Pond turnover = fast against bioconverters and filter flow rates = slow

What the difference is – how to achieve it in practice

CONTINUUM – Bioconverters and some (not settling chambers or

vortexes) filters have materials in them that are referred to as

media. The media performs different functions in filters and

bioconverters. Media is the heart of the bioconverter. Chapter 3:

Media …………………...KHA Program – Filtration Module 27

CHAPTER 3: MEDIA

Definitions

A media chamber is defined as a surrounding environment in which

something functions or functions and thrives.

Media in a bioconverter is the substance in which and/or on which the

organisms that perform the bioconversion live and thrive.

Basic Principles

1. Media can be used in the bioconverter or in the filter. The term

media applies to both utilisations.

2. Used in a filter, the media is there primarily to provide some

sort of barrier to the passing water. This barrier assists in the

trapping of solids.

3. In a bioconverter the media is used to increase the available

surface area for the bacteria that perform the function of

nitrification to grow on. Media also traps "food" particles for the

organic digesters to work on.

4. There are a host of bacteria growing in the bioconverter not only

nitrifying bacteria but heterotrophs. All of these need space.

Their living space must also be taken into account when designing

a bioconverter

Types of Media

1. Stone - natural rock, gravel and sand must be inert & not affect

the hardness of the water in any way. Occasionally other media

such as marble chips, zeolite and oyster shells are used to

intentionally increase the hardness and used as a media as well.

2. Ceramic – clay that has been fired at a very high temperature. It

is sometimes porous. Available in various shapes such as spheres,

stars and hollow cylinders.

3. Plastic beads – usually spherical shaped solid balls of plastic

material.

4. Plastic shapes – plastic media is available in a wide variety of

shape from extruded and cut shapes to injection moulded shapes.

Plastic matting – random fibers of plastic thermally welded at

points of contact.

5. Plastic foam – open cell polyurethane foam

6. Brushes – usually plastic bristles with stainless steel wound.KHA Program – Filtration Module 28

centre wires.

The Bioconverter

The bacteria that colonise our bioconverters are unique in that they

have to be attached to something. They are not free floating. This fact

dictates that their food and oxygen must be brought to them. They

cannot seek their own nourishment.

This leads us to reach other conclusions. The bacteria that grow on and

inhabit the surface area provided in the bioconverter are microscopic.

Therefore, the water laden with the food (ammonia) and the oxygen

should come into contact with the microscopic layer of bacteria by not

being too far away.

Another conclusion can be drawn from the fact that the bacteria

adhere to the surface area is that the water passing by should move

continuously. In other words the pump or pumps must run 24 hours a day

to bring the necessary nourishment into contact with the bacteria.

As the water passes the bacterial colonies they oxidise the ammonia to

nitrite in the presence of oxygen. Other species of bacteria oxidise the

nitrite to nitrate, also using the oxygen in the passing water.

Bioconverters compete with the fish in the pond for the oxygen in the

pond water to do their job of converting ammonia to less toxic

substances. Bioconverters work better at high levels of oxygen. Koi are

healthier at high levels of oxygen. Therefore, high levels of oxygen

should be maintained through out the system.

The bioconverter virtually becomes a living entity after it matures. It is

home to millions upon millions of bacteria and micro-organisms that are

working in our favour by purifying the passing water. It is critical to

keep this in mind as the filter may be damaged when we add chemicals

to the pond water to treat the fish.

Nitrifying bacteria grow on the surface area of the media in the

bioconverter but so do a host of other organisms. Including

heterotrophic bacteria that consume organic matter.

Some studies indicate that the heterotrophic bacteria can, and often

do, take up much more space than the nitrifying bacteria. So provision

has to be made for all the life forms supported by the bioconverter.

Media

The material we use in the bioconverters to provide a surface area for

bacterial growth is called the media. The media is the heart of your

recycling system. The success or failure of the whole system is

dependant, to a large extent on the media. (size, depth, type of material

etc.).KHA Program – Filtration Module 29

A huge variety of materials can be used as bioconverter media. It is

critical that the media must be inert and not affect the water quality in

any negative way. Always be sure all materials are non-toxic and will not

produce chemicals that will be harmful to the fish. And, it’s a good idea

to thoroughly wash the media before use in the filter.

Stone, gravel, plastic of any description, nylon hair curlers, pot

scourers, shade cloth netting, etc. etc. can be used as media. Clay beads

make excellent filter media material. Lava rock has many minute pores

and a massive surface area for bacterial growth.

Lava rock in small, golf ball size pieces, makes an excellent bioconverter

filter media. Large pieces of lave rock can also be used but it is difficult

to clean w/o breaking off pieces of the rock. And large pieces of any

media allow unwanted channelling. A sample of the lava rock to be used

must be boiled before use to test if there are no chemicals such as

sulphur in it.

Ceramic by-products that look like coral are emerging on the market.

They are excellent filter materials but with similar shortcomings to lava

rock.

A media with a rough surface makes a more hospitable place for

bacterial colonies to establish themselves and additionally, has a larger

surface area. Media with rougher surface areas can withstand rinsing

with less damage to the bacterial biomass but also retains some

detritus.

Plastic in various forms is extensively used as a media. Plastic is

convenient and light to work with. One draw back is that it can be very

expensive. Another is that the microscopic surface provided by plastic

for nitrifying bacteria is often very smooth. Unless the bioconverter

has an efficient up-stream settlement tank or mechanical filtration of

some sort to remove the solids before the bioconverter media, it must

be capable of dealing with the debris load. The hollow spaces in plastic

rings make wonderful areas for accumulating waste solids.

Media Surface Area

The surface area of bio converter media is important. This is the total

surface area available in the bio converter for bacterial species to grow

on. Not only nitrifyers grow in the bioconverter but also a host of

heterotrophs. The nitrifyers convert the ammonia to nitrite to nitrate

and the heterotrophs consume the organics that become trapped in the

filter media.

Obviously media with a rough surface would be more habitable for

bacterial growth when compared to a smooth surface.

The total surface area for bacterial growth in a bioconverter is.KHA Program – Filtration Module 30

increased (even if media with a small surface area is used) by increasing

the volume of the media.

The volume can be increased in two ways. Firstly, by increasing the

depth of the media. In this case, the flow through rate will remain the

same. Or, increasing the size of the chamber through which the water is

passing will spread the media out (keeping it shallow). The direct

consequence of this is that the water flow rate past the bacteria will

slow down.

Media with massive surface areas can mean smaller bioconverters can be

built. However, smaller bioconverters will have very fast water flow

rates. Therefore, a compromise must be found between massive surface

areas of media (small bioconverters) and the very fast flow rates that

will either scrub the bacteria off the media or remove their food supply

before they can utilise it.

Hydraulic Loads on Media or Even Flow

Hydraulic load or even flow can be defined as the even movement, over

the whole bioconverter chamber, of water on the interface between the

media and the passing water. Once the water enters the bioconverter

chambers it is essential that the water has an even flow through and

past all the media. In other words the water passes evenly through the

media with out channelling. Any channelling makes the bioconverter less

efficient.

In open trickle filters the hydraulic load will be even as the water is

sprayed over the top layer of media and it trickles evenly down as a thin

layer of water through the filter media.

Up flow bioconverters must be designed in such a way as to ensure the

water moves evenly upward through the media.

In up-flow bioconverters, a grid to suspend the media off the floor will

ensure the hydraulic load is even. The open chamber underneath the

media makes flushing easier.

Physical Lay-out of the Media

The way the media is packed inside a bioconverter chamber can have a

significant influence on its efficiency. It is critical that little or no

channelling takes place in the media. Any channelling will result in water

by-passing a portion of the media and the bioconverter becoming less

efficient.

Media beds with channelling could mean sections are deprived of oxygen

rich water. Such areas may die and become anaerobic producing smelly

and toxic hydrogen sulphide. Further, channelling will allow a portion of

the pond water returning to the pond with the impurities it brought into.KHA Program – Filtration Module 31

the filter chamber in the first place.

Effects on Flow Rate with Different Media in Different Chambers

Different media will have different flow rate characteristics. When

packed, some media have smaller openings between the pieces. An open

media will have less flow restrictions than one with smaller openings.

Chambers with different media can have a greater or lesser tendency to

‘back up’ or clog due to their different flow characteristics.

Depth of Filter Media

Whilst it is anticipated that deep filter beds will have less and less

oxygen in the levels far from the inlet, there is much evidence that this

phenomenon is insignificant in most instance.

As ammonia and oxygen rich water passes media with nitrifying bacterial

colonies growing on them, the ammonia will tend to be removed in the

presence of the oxygen. Although this is done immediately on contact

the bacteria do have a finite ability in this regard. Thus any residual

ammonia flows on to the next colony and to the next, etc. Also any

ammonia or oxygen not used by the bacteria simply passes on to the

next part of the system.

When the bacteria in the lower areas of the bioconverter are saturated

with ammonia their needs are minimal and the excess ammonia passes to

the next portion. As soon as they need nutrition they begin the

oxidation process again. This is an ongoing and dynamic process in the

media bed and should not be viewed as an on – off type of situation.

One problem that is encountered with deep media beds is the build-up

of organics and the subsequent difficulty in cleaning (see: Pond Design

section for ideas on how to clean filters effectively) It is anticipated

that filters will remove much of the solids in the pond water before the

bio converter, however reality suggests that there will always be a small

amount of solids passing into the bioconverter.

CONTINUUM – Koi Ponds produce vast amounts of organic

material. Solids in the form of dust and pollution are continually

added. Pond water needs to be cleared of these solids so the

bioconverter can operate as efficiently as possible. Chapter 4:

Filtration …………………...KHA Program – Filtration Module 32

CHAPTER 4: FILTRATION

Whilst bioconversion removes ammonia etc., there are various other

forms of filtration – mechanical removal of solids, settlement, DOC

removal. They have basic principles governing them.

Basic Principles

1. The purpose of filtration on a koi pond is to remove solids from

the water. Removing various solids results in clear water. Clear

water allows us to see our koi.

2. There are various methods of filtration. From settlement to

vortex action to screening.

3. Generally speaking, slowing the water down through the filtration

part of the system will assist with removal of solids. However in

true vortexes, water is sped up to assist with the elimination of

solids.

4. Solids in water are in various forms. The most common in ponds is

algae. All ponds will produce algae to a greater or lesser degree.

Algae is organic material. When it is trapped in the filter or it

dies and enters the filter, it will decompose. Decomposing algae

(organic material) has a negative effect on water quality. It will

remove some oxygen and it will add some ammonia.

5. Filtration is the high maintenance area of the pond. Filtration

design should take this factor into account.

6. No matter how complex or how simple, the filter and settlement

areas must be maintained regularly. This fact is critical for

maintenance of water quality.

7. Filters are often attached to ponds before the bioconverter to

ensure the water is as free of solids as possible. This is to

prevent the bioconverter from clogging and becoming inefficient.

Mechanical Filters

All mechanical filters are used primarily for the entrapment of the

various solids found in koi ponds. They can be incorporated almost

anywhere in the filtration system.

Various types of mechanical filters -.KHA Program – Filtration Module 33

1. Settling – debris heavier than water.

2. Settling aided by centrifugal and/or differential hydraulic

forces

3. Mechanical exclusion – screens, fabrics, sand floating media

other matrixes of small holes – physical straining.

4. Mechanical entrapment - (brushes, matting, floss, floating

media, rocks, sponge, sand beds, stone beds etc)

5. Circular-flow – vortexes (not really vortexes but called that by

the people who make them)

Types of Media used in Mechanical Filters

1. Stone - natural rock, gravel and sand.

2. Plastic – beads usually spherical shaped solid balls of plastic

material.

3. Plastic foam – open cell polyurethane foam.

4. Plastic shapes - extruded and cut shapes, injection moulded

shapes.

5. Plastic matting - random fibers of plastic thermally welded at

points of contact.

6. Brushes - usually plastic bristles with stainless steel wound

centre wires.

7. Screening – woven screen usually stainless steel or plastic.

Filters can be open or closed in design, i.e. closed are under pressure.

Open Mechanical Filters

Open mechanical filters can have the water gravity-fed through them

and therefore, need specific design considerations for water levels.

Open mechanical filters can also have the water pumped to them and

forced through the chamber or chambers. This design can have the

placement of the chambers almost anywhere (above pond water level) as

the water will have gravity flow back to the pond. Sucking the water to

the pump then pumping it to filters is less efficient at removing fine

solids as the pump impeller creates more fines by macerating the solids.

Closed Mechanical Filters

Closed mechanical filters are dependent on water pumped from the pond

through the container. Closed or pressurized filters can be almost

placed anywhere..KHA Program – Filtration Module 34

1. Sand Filters (variations of pressurized or swimming pool sand filters)

see sand filters.

2. Floating bead filters – (also used as mechanical filters).

3. True vortex filters – closed system with fast spinning water.

4. Cartridge filters – media is in cartridge form, is generally removed and

hosed off for cleaning.

5. Bag filters – fine mesh bag – can be a long tapered ‘sock’ stuck into a

large diameter pipe.

Settlement Out Side The Pond

Settling Chambers

Areas or containers outside the pond where the water is slowed down.

For settling tanks to be effective, they need to be large so that the

water passing through them is forced to slow down. Alternatively, they

have to have some type of baffle arrangement to screen the passing

water. In most cases, large chamber with baffles are used.

As the water slows down, the solids settle out. The larger the settling

chamber the more the water will slow down. If the water could be

brought to a complete standstill a very high percentage of the solids

could be settled out. However, this would require settlement tanks

larger than the pond its self. If space is at a premium other types of

settling tank designs can be used.

Gravitational settling is a process by which solids denser than water

eventually drift to the bottom of the chamber under force by gravity.

The settling tank is there to help slow down the rate of clogging of the

pump and/or bioconverter. By placing the tank or basin so that the pond

water flows through it before entering the biological filter, you can

reduce - but not eliminate - the rate of clogging in the bioconverter

itself.

Settling Basins and Discharge Boxes

See KHA – Pond Design section by Burt Ballou for more complete

information on these design features.

It is critical that the discharge box, which is designed to collect solids

before the pump and filter medium, have some method of easily flushing

the solids to waste.

It makes no logical sense what-so-ever to collect solid waste in this area

and then make it impossible to flush or clean! An outlet, directly to the

storm water drain or garden should be installed in the discharge box.

Valves or stand pipes to close off the pond and the filter boxes or.KHA Program – Filtration Module 35

chambers are necessary. The discharge box or settlement tank should

be totally isolated and thoroughly flushed when necessary as this is the

area of the filter system which will require the most regular

maintenance.

Organics that collect in any part of the pond system will bio-degrade

and negatively affect water quality.

Sand Filters

Pressurized containers – sand filters – that are utilized on swimming

pools are sometimes used on koi ponds for removing solids and also as

bacterial bioconverter areas.

High rate sand filters are designed for use with chemically treated

water. This point is important to remember. In a swimming pool, after

chemicals have been used, the algae and micro organisms in the water

die. This results in their cell structure collapsing. The collapsed cells

take up less space. The chemicals poison the organics in the water so

they take days or weeks before they start to grow again; therefore, the

load on the filter is minimal. Under these circumstances a single sand

filter will be adequate for the average swimming pool.

In our ponds the situation is totally different. Organic substances and

micro organisms in the water are produced continually. Algae is a major

source of solid organic pollution in the pond. Therefore, we have to

change the parameters for the use of high rate sand filters on koi

ponds from the way they are used on swimming pools.

The most important limiting factor of sand filters is that they are

highly restrictive of flow rates. The fine sand or gravel in the bed and

the limited surface area of the sand bed itself, as well as the size of

the pump used limit the flow rate. The multiport valve that is standard

equipment on such filters also restricts flow rates. The rapid build up of

organics in the sand bed further restricts flow rates.

Taking the above into account, we have to "redesign" high rate sand

filters for koi pond applications. It is critical to maintain flow rates in

koi pond situations and sand filters need frequent back washing.

A single high rate filter works very well on a small pond but on large

ponds they are effective only for a limited time. The larger the pond

volume the quicker a single sand filter will clog up. This in turn means

frequent maintenance by backwashing. Higher stocking densities in any

pond make regular cleaning of the pond filter system essential.

Daily removal of solids can be overcome by having two or more sand

filters IN PARALLEL.

With two or more sand filters in parallel, the water moves through

several multiport valves (far less restriction) and then several sand.KHA Program – Filtration Module 36

beds at the same time. The flow rate is greatly increased but the

filters still do their job.

When the filters are back washed each filter must be backwashed

separately. This gives maximum flushing capacity to each sand bed.

Sand filters are sometimes by-passed. If this is done for any longer

than a day or so it is absolutely necessary to remember to back-wash

the filter before it is used on the pond again. The water trapped in the

chamber is cut off from the oxygen in the atmosphere. It will become

anaerobic within a very short time. Large amounts of anaerobic bacteria

are not healthy for the koi and should not be pumped to the pond.

Anaerobic conditions can be detected by a very obnoxious smell.

Sand Filter Use Summary:

High rate sand filters are very efficient mechanical filters. Efficient

mechanical filters trap solids in a convenient place. The more solids that

are removed from the passing water the quicker any mechanical filter

will clog up. But the result will be clear water but a filter that needs

frequent cleaning.

Consideration must be given to using more than one sand filter on larger

ponds. These must be in parallel so that the system will benefit from

improved flow rates because the restrictions from a single sand bed and

a single multiport valve and restrictions in the arms will be eliminated.

This results in large surface areas of mechanical and biological filtration

and extended time between backwashing.

Bypassing sand filters for any length of time allows anaerobic bacteria

to grow in the chamber. The filter must be flushed before being used on

the pond.

Sand filters need high-pressure pumps. These are more expensive to run

than other types of pumps.

The use of sand filters does not seem to allow the heterotrophic

bacterial colonies to form properly (probably because of the frequency

of backwashing) and thus a UV light is required to stop green water.

Even the UV won’t stop the string algae from forming – big filters will.

CONTINUUM – The liver (the heart is the pump see p. 7 of this

doc.) of the koi pond is the bioconverter. Bioconverters are

critical for the successful functioning of a koi pond. Chapter 5:

Bioconverters …………………...KHA Program – Filtration Module 37

CHAPTER 5: BIOCONVERTERS

Basic Principles

While the function of the filter is to remove solids from the pond

water, the function of a bioconverter is to utilise natural organisms such

as bacteria to complete the nitrogen cycle by converting ammonia

(symbol NH3 - highly toxic to fish) to nitrite (symbol N02, also toxic to

the fish), to nitrate (symbol NO3) not toxic to koi except at very high

levels, to free nitrogen and nitrous oxide.

The excretion of koi is mostly ammonia via the gills and some solid

faeces. This excretion is toxic to fish and has to be removed as quickly

as possible. As the fish are excreting their bodies metabolic waste by-products

throughout the day, the ammonia must be removed all the time

by continuously running the pumps.

Ammonia is found in two forms in ponds, ionised and unionised forms.

The higher the pH and temperature, the higher the percentage of the

toxic or un-ionised fraction.

The ammonia gas dissolved into the water dissociates into ammonium,

NH4+ (the + denotes it's an ion) and ammonia, NH3. This dissociation is

something Mother Nature does based on the laws of physics and

chemistry. How much is in each state is a function of temperature and

pH (as far as we are concerned).

At a pH of 8 for example, and a temp of 20Ί C all the ammonia dissolved

into the water dissociates into 98% ammonium and 2% ammonia.

As the nitrifying bacteria that grow in the bioconverter convert

ammonium to nitrite to nitrate, the pond system is purified - if the

filter is adequately sized and sufficient water is flowing through it.

Effects of High Levels of Ammonia

The amount of ammonia produced by the fish is approximately 0.03 x

feed. Therefore, for every 1000g (about 35 ounces) of feed that is fed,

30g (about 1 ounce) of total ammonia is produced. This is excreted by

the fish primarily from the gills and to a lesser degree in the urine.

The ammonia production will vary throughout the day with the highest

values occurring about two hours after feeding. However, this is

temperature dependent.

High ammonia levels in the water mean that the fish cannot excrete the.KHA Program – Filtration Module 38

ammonia from its body through the gills. The ammonia builds up in the

blood, poisoning the fish. Fish can often be observed breathing much

quicker or crowding round inlets (where the ammonia concentrations are

less and oxygen concentrations highest) in an effort to get rid of the

ammonia from their systems.

pH and Ammonia

An increase in the pH of a single unit increases the toxicity (amount un-ionized)

by a factor of 10, regardless if the starting pH is 7 or 7.5 or 8

or whatever. It is essentially logarithmic in this regard over the

temperature and pH regions we are involved with in koi ponds.

Bioconverters

The bioconverter virtually becomes a living entity after it matures. It is

home to millions upon millions of bacteria and micro organisms that are

working in our favour by purifying the passing water. It is critical to

remember this, as we often do not realise that the bioconverter may be

damaged under certain conditions. For example when we add chemicals

to the pond water to treat the fish. Or when the pumps as turned off

for any length of time.

The bioconverter is home to various bacteria species doing different

functions to support their life forms.

Nitrifying Bacteria

Bacterial species found in nature that oxidise ammonia to nitrite and

then nitrate. These are chemolithotroph species of bacteria that live in

an oxygen rich environment, utilize mostly inorganic (without carbon)

compounds as their energy source, and require carbon dioxide (CO2) for

their source of carbon.

The nitrifying bacteria that oxidise ammonia to nitrite have an optimum

pH range of 7.8 - 8.8. The lower limit for reasonable growth for

nitrifying bacteria is given as pH 7.0 - 7.6. While the upper limit is 9.4.

Around pH 6.5 nitrifying bacteria cease to function.

Historically, Nitrosomonas & Nitrobacter are the names used for the

bacteria suspected of converting ammonia to nitrite to nitrate in our

bioconverters. Recent studies have produced evidence that these

nitrifying bacteria are not present in bioconverters in large numbers.

Nitrospira bacteria have been identified as being responsible for doing

most of the converting of nitrite to nitrate. Work is currently underway

to identify the bacteria, suspected to be a Nitrospira as well, which

converts ammonia to nitrite.

A microbiologist in the 40's identified Nitrosomonas and Nitrobacter as

two types of bacteria responsible for nitrification in soil and stated.KHA Program – Filtration Module 39

that "probably the same were in the water environments". For the next

20 years or so, his original paper was continually referenced and new

authors stated that "probably" it was Nitrosomonas and Nitrobacter.

Then the reference and the terminology "probably" basically

disappeared from the articles and it became a known "fact". This "fact"

now seems to be being disproved.

Heterotrophic Bacteria

Heterotrophic bacteria are generally considered to be organic sludge

degraders. An organism that is termed heterotrophic (e.g.

heterotrophic bacteria) is one that gets its energy from the intake and

digestion of organic substances.

All animals get their food this way, through the consumption of plants

and other animals, however the term is more commonly used to

distinguish between the different types of bacteria that are found in

ponds and biological filters (bioconverters).

The heterotrophic bacteria are those that lower the BOD (biological

oxygen demand) of the water by consuming the dissolved and particulate

organics from the faeces of the fish (and algae as well as all other

organics). These bacteria are distinguished from the nitrification

bacteria that use the ammonia and nitrite for their energy source. (The

heterotrophs require organic carbon; chemolithotrophs get their carbon

from carbon dioxide).

Some heterotrophic bacteria are facultative anaerobes - meaning they

can function with or without oxygen. They will do completely different

functions depending on the level of dissolved oxygen present.

The heterotrophic bacteria appear when a food source is available (i.e.

algae growth). They tend to disappear when the food source is

consumed.

Under optimal growth conditions, nitrifying bacteria can double in

population every hour or so. Heterotrophic bacteria, on the other hand,

can reproduce in as little as 15 minutes to 1 hour.

Starting up Bioconverters

A new bioconverter, no matter how large or complex, is not functioning

when it is started up or after a pond has been treated with certain

chemicals. The various bacteria required to convert the impurities from

the fish are simply not there. Some bacteria start growing immediately.

But again, there are not sufficient numbers available.

This start-up period of a new pond can be very tricky. The water is in,

the pumps are running, you have spent a great deal of money on new koi.

The food is bought and the fish are fed. Immediately there will be a.KHA Program – Filtration Module 40

build up of ammonia. Each time the koi are fed this level of ammonia will

increase. Nothing is available in the pond / filter system that will

remove this ammonia.

As ammonia is not only toxic to koi at high levels but it is also stressful

to koi at very low levels, precautions must be taken in the start-up

period of a pond.

Therefore, it is a good idea to shorten the start-up time of

bioconverters.

Seeding Filters

One of the easiest methods of kick-starting a bioconverter is to seed

the media with some media from another, reliable established

bioconverter. Another method is to place some clean out from a good

active bioconverter into the inlet of the new filter.

On each piece of media in a mature bioconverter will have literally

millions of bacteria growing on it. By placing some of this media, even a

few handfuls, in the new bioconverter media, this will seed the new

filter.

By seeding the filter you will have placed colonies of the various types

of nitrifying bacteria directly into the media. These will spread and

multiply rapidly giving a rapid start-up of the bioconverter.

Open Bioconverters (Open media systems)

Bioconverters that are not sealed and operate under pressure are

termed open bioconverters. These can be up-flow, down-flow or

horizontal bioconverter are ones in which the water flows up-wards,

downward or horizontally, respectively, through a material – the media -

which is utilized primarily for the growth of nitrifying bacteria - and

other beneficial bacteria.

Other types of open bioconverters

1. Integrated Vortex type

A vortex bioconverter is a container / area / locality / where, by the

nature of its design, the water flows in a circular motion (usually before

entering the media and at the bottom of the container) to settle solid

matter to the centre for easy removal.

2. Trickle Filters

A trickle bioconverter is - a container / area / locality / where, by the

nature of its design, the water flows openly (gravity fed) down-wards as

a film over a media (a material which is utilized primarily for the growth

of nitrifying and other beneficial bacteria)..KHA Program – Filtration Module 41

3. Fluidized Bed Filters

Water flows upwards through the media and the velocity of the water

pushes the media particles up into the container. This causes them to

rise. As the water velocity increases, the particles rise higher in the

column, expand and become more fluidised.

Fluidized Bed Filters usually have sand or small plastic particles for a

media. This substrate allows bacteria to adhere to it and grow. The

constant movement of water and particles in the chamber ensures that

there are no dead spots. The velocity of the water is controlled so that

as the particles collide, they do so with just enough force to knock off

any excessive or dead bacterial floc.

Air can also sometimes be used to assist in the fluidising process,

especially where water velocities are too low to obtain sufficient

fluidising. The use of sand can be problematical. The weight of the sand

makes it difficult to achieve an even bed fluidisation. However if the

water flow stops, the sand packs down suffocating the bacteria rapidly.

Plastic media are easier to fluidise.

7. In Pond Filters

Bioconverters and filters are occasionally incorporated inside the pond.

Here a gravel or stone bed is used on the floor of the pond or in a

section of the floor area.

A grid of pipes under the media bed is used to suck the water to the

pump thus pulling the pond water through the filter.

These filters/bioconverters work in exactly the same way as other

biological filter. However, as the media is at the bottom of the pond

organics are drawn into the bed and clogging will be rapid. Once the bed

becomes clogged, it has to be cleaned or it will become anaerobic and

poison the entire pond.

The only way an in-pond filter can be cleaned properly is by draining the

water and cleaning the media. Alternatively the whole media bed can be

shovelled out and cleaned with pond water. Although many are still in use

this makes in-pond filters impractical and possibly a danger to koi.

Closed bioconverters (close or pressurized systems)

The majority of the closed or pressurized bioconverters are sealed

containers where, by the nature of its design, the water flows through

media.

1. Floating bead bioconverter

A floating bead bioconverter is one in which the water enters the

container at either the bottom or near the middle of the unit and rises.KHA Program – Filtration Module 42

upward toward the exit. The bead media (usually plastic) floats in the

top of the chamber. A biofilm forms on the floating beads. This film

acts in two ways: 1) to nitrify the ammonia and 2) because of its ‘sticky’

nature, it tends to also act as a mechanical filter to trap solid debris.

2. Sinking media bioconverter

This group includes any chamber capable of being pressurized that

contains media heavier than water thru which the water passes and is

made less toxic by the function of the organisms living in and on the

media. Examples of such bioconverters are: sand filters, sand filter

housings with the media changed to one more open like balance and

chambers with matting media like Japanese matting or Matala mat.

Fludized bed filters can also be operated in a pressurized chamber,

3. Combination bioconverters

Bioconverters that contain both sinking and floating media are found in

some designs. In one commercial embodiment, sinking beads are used as

a fluidised bed for bioconversion and the floating beads are used as a

mechanical filter. One of the unusual things about this combination is

that the water enters the bottom of the filter and passes through the

bioconverter portion first. Because that bed is fluidised, no debris is

collected there but rather it passes on thru to the second stage of the

unit where the floating beads trap the solids.

Bioconverter and Filter Size

The conversion of ammonia to nitrite to nitrate is a performed by

microscopic bacteria that grow on the all the surfaces in the pond

system. However, they are concentrated in the bioconverter. This is the

area designed to provide a large surface area for them.

The conversion of ammonia to nitrite to nitrate occurs instantaneously

on contact with the nitrifying bacteria. If the ammonia molecule is some

microscopic distance away from the bacteria, no conversion will take

place.

Key factors dictating bioconverter size

As the ammonia load increases, more bacteria are needed not more time

for conversion. Flow rates are directly related to this. Therefore, the

amount of functional surface area available to the nitrifying bacteria is

of importance.

Certain media have enormous surface areas but their full potential

cannot be realised as the greater the specific surface area, the less the

volume of media required. The less media utilised the smaller the media

chamber. The smaller the media chamber the faster the water will move.KHA Program – Filtration Module 43

past the media.

Very high velocities of water can remove the nitrifying bacteria from

the media. Consider the flow rate through a pressurized bioconverter

compared to that of a typical up or down flow bioconverter. Even during

backwashing, nitrifying bacteria are not significantly removed although

the heterotrophs and their food supplies (organics) are.

Surface Area – Projected and Total

Projected or Cross-sectional Area of the Individual Chambers

Individual chamber projected or cross-sectional surface area (of a

square or rectangular chamber) is the length x the breadth of that

chamber for up or down flow conditions.

Projected or Cross-sectional Area of the Complete Bioconverter

The projected or cross-sectional surface area of the bioconverter is

the combined projected surface area of all the individual chambers.

Each chamber should have a flow rate through it that is properly

determined by its surface area. For a given throughput, the smaller the

projected area of the chambers, the faster the water will flow and

conversely, the larger the projected area, the slower the water will

flow. The specific flow is the flow rate per unit of projected surface

area.

Total Area of the filter material or media

The surface area of different media can vary greatly. Some ceramics

advertise a phenomenal 10,000 m 2 /m 3 . Aquarium gravel has around 700

m 2 /m 3 . Plastics have between 100 and 1500 m 2 /m 3 .

Whilst very large surface areas may be attractive, the flow rate

through the whole filter system and contact time must still be

considered important.

Effects of different media on flow rates

Different media pack differently in filter chambers. The shape and the

size have a direct influence on the flow through the chamber.

Having chambers with different void spaces can lead to problems. If the

water is pushed through a multi chambered filter system and the second

chamber has less void space than the first, back-up and overflowing will

be experienced in the first chamber.

If the pump is sucking at the end of a multi chambered system and

chambers with different media are used then the chamber with the

least void space may be pulled dry..KHA Program – Filtration Module 44

Contact Time within the Bioconverter

Nitrifying bacteria convert ammonia to nitrite to nitrate virtually

instantaneously. The flow rate through the bioconverter is usually

slowed down in an attempt to get 100% conversion in one pass through

the media by having ALL the water come in contact with the media in a

single pass.

The flow rate through the whole pond system should be relatively fast.

The flow rate through the bioconverter should be slowed down without

affecting the overall flow rates. Increasing the size or number of the

filter chambers in the system and running multiple chambers in parallel

achieve this.

It is generally agreed that faster flow rates through bioconverters are

more beneficial than slow flow rates.

Shutting Down Filters

Generally speaking it has been thought that shutting down filters for

even a short time is detrimental to the nitrifying bacteria. However,

there is some evidence this is not the case, provided the media is kept

damp if the chamber is drained or provided the water around the media

does not become devoid of oxygen if the water is kept in the chamber

or chambers.

Nitrifiers are very patient - when the situation changes to something

they don't like, they generate a lot of EPS (exo-polymer substances) for

protection and go into a kind of hibernation waiting for the conditions to

change for the better. They can wait a long time.

DAMAGING BIOCONVERTERS

Bioconverters are living entities and can be damaged. The addition of

chemicals to the pond water often damages the biomass in the filter.

Some chemical do more damage than others. Antibiotics will not only kill

bacteria in the pond but will kill the bacteria in the bioconverter as well.

The pH of the water affects the nitrifying bacteria. Pond water pH

should be between about 7.0 and about 8.5.

The ammonia given off by the fish is processed into the much less toxic

nitrate (passing from ammonium to nitrite to nitrate). However, while

processing the fish waste, the filter produces acid that tends to lower

the pH of the system.

If the pH drops precipitously below about 6.8, the bacteria stop working

and the waste ammonia is unprocessed - this is known as a ‘filter crash.’

If the problem isn't fixed and fixed correctly, the fish will die.

To prevent filter crashes, keep the alkalinity up so the water is.KHA Program – Filtration Module 45

buffered against the acid that the bioconverter bacteria constantly

produce.

CONTINUUM – Koi Ponds produce vast amounts of organic

material. Solids in the form of dust and pollution are continually

added. These substances are removed from the pond water in the

filters. The filters have to be cleaned regularly or the passing

water will come into contact with the decomposing organic matter

trapped in this area.. Chapter 6: Maintaining Bioconverters and

Filters …………………..

CHAPTER 6: MAINTAINING BIOCONVERTERS AND

FILTERS

Basic Principles

Having a water feature means accepting responsibility. Our

responsibility is to keep the water in the feature healthy. If we neglect

the pond, the koi will suffer and we will also suffer. The pond,

bioconverter and filter system has to be cleaned regularly - let's

make it easy to do!

No matter how sophisticated a system is or how expensive it is, the

reality is that if it is not properly maintained, the system will

degenerate to the point where the fish will die.

Design good mechanical filtration so that the bioconverter bed is

seldom disturbed. The longer the bed remains undisturbed the greater

the biomass that will grow. This in turn means the converter will be

more efficient at processing the impurities that flow through it.

However, reality dictates that no matter how efficient the mechanical

filtration is, the bioconverter will still need cleaning from time to time.

Mechanical filtration will always require more attention than the.KHA Program – Filtration Module 46

biological filtration. Therefore, the mechanical filter must be as easily

accessible and designed for ease in maintenance.

Bottom drains are sometimes designed to flush bottom water to waste

only. Therefore, stand pipes must be drawn regularly to avoid the water

trapped in the bottom drain from becoming anaerobic. In this case it is

better to connect the bottom drains directly to the pump (although it is

not always recommended) or directly to a discharge box so that the

water is drawn continuously through the piping.

Cleaning Ponds & Filters

Maintenance

Lack of maintenance – the root of all evil?

One of the major causes of fish disease problems is lack of pond

maintenance by pond keepers. Nature is working 24 hours a day, every

day of the year. Algae (organic material) constitutes the bulk of the

solid build-up in pond systems. This organic material will decompose. If

it is allowed to build up, it may be cut off from the passing water and

become anaerobic. Anaerobic bacteria produce hydrogen sulphide – this

is toxic to fish.

Run your hand over a tabletop in the house for example, and every day

there is a film of dust. Exactly the same continuous pollution, in various

forms, is settling onto and into our ponds. Ponds are literally giant

settlement chambers.

Backwashing Bioconverters and Filters

The pond keeper has to familiarize himself with the maintenance side of

the system components. Many problems in water quality can be ascribed

to poor maintenance (and often poor design which makes maintenance

difficult). Each pond will be slightly different with regards to what

needs to be done to keep the water pure and clear.

It is absolutely essential to make provision to have some method of

cleaning pond filters - easily and thoroughly. Bioconverters should be

cleaned less frequently. The use of pond water to avoid damaging the

biomass with chemicals often found in tap water is recommended.

Primary Design Features for Successfully Cleaning Filters

It is a fact of life that all pond filters will clog to some degree at some

time or other. Therefore, design the filter to be easy to maintain -

when the need arises.

For more details see KHA – Pond Design section by Burt Ballou.KHA Program – Filtration Module 47

Cleaning and Damage

Biological filter media that is removed can be kept moist at all times

with pond water. This will keep the bacteria active. When washing filter

media try to use pond water. This will avoid damage to the bacteria

from chemicals in tap water.

The debate on the damage to the filter bed if it is turned over a few

times a year to rinse away the excess solids is often exaggerated. The

results of having the filter bed clear of organic and solid material far

outweighs the damage done by the occasional washing it requires.

Most of the bacteria washed way will be the excess and/or dead

bacteria. Provided the filter media is kept moist whilst back washing and

turning, the damage is minimal. The bacteria being established in vast

numbers in the filter bed will spread through the entire filter bed very

rapidly once the system is started up again.

The secret is to use pond water if possible, and not tap water. Tap

water contains chlorine and other additives that will kill many bacteria it

comes into contact with.

How Often Should Filters be Cleaned?

As often as is necessary to maintain good clear water quality. Your

personal circumstances will dictate the frequency of cleaning the filter.

The more frequently solids are removed from the mechanical part of

the filtration system, the clearer and more healthy the water will

become.

The less frequently the biological converter is cleaned or disturbed,

the stronger the biomass will become. (This statement is subject to

the bioconverter being free of solids).

Although these two statements are generalities and seem to contradict

each other, it is a fact that by regular cleaning and flushing the

chambers and media the fish will be healthier over a longer period of

time.

Water Changes (water changes out)

Irrespective of the size and complexity of the pond filtration system

we cannot escape the fact that we have to add fresh water from time

to time to our ponds. The mere fact that there is some degree of

evaporation and also water loss when cleaning the filters makes it

necessary to top up the pond.

Water changes should be done regularly in ponds as the environment is

always deteriorating to some degree - no matter how large or complex

the filter system is. Many enthusiasts advocate a 10% water change per.KHA Program – Filtration Module 48

week. The author considers this to be a minimum.

Regular water changes have advantages:

•various by-products of the pond system such as nitrate and

phosphate build-up, DOC concentrations, pheromone levels

etc. will be diluted.

•solids (suspended and dissolved) will be removed.

•essential trace elements and minerals will be replaced.

Fresh Water Caution

Tap water usually has chemicals added to it. Chlorine and chloramines

can be deadly to koi. These chemicals can burn the gills of koi and

suffocation may result.

Well or borehole water usually does not contain any oxygen and placing

koi directly into fresh well or borehole water can result in sever stress

and even death.

See: Water Quality section by Norm Meck for details and solutions.

CONTINUUM – There are many methods of removing ammonia we

discuss some of them in. Chapter 7: Alternative Methods of

Filtration and Bioconversion ………...KHA Program – Filtration Module 49

CHAPTER 7: ALTERNATIVE METHODS OF FILTRATION

AND BIOCONVERSION

Ion Exchange - Zeolite

The most commonly found ion exchange medium in aquaculture is zeolite

material. Zeolite has positive ions held within a silicate lattice. The

ammonia and other negative ions in fish waste water are taken up by the

zeolite and bound into it's structure.

Flushing with solutions such as sodium chloride or sodium hydroxide can

then recharge the zeolite. Zeolites can maintain a high level of

effectiveness if recharged correctly.

Zeolite is a unique substance. There are over 40 natural zeolites and 150

artificially made ones. Zeolite is literally a sieve on a molecular or

atomic scale. Zeolite can be used to remove ammonia directly from the

water, or as a biological filter medium. Zeolite can reduce water

hardness. Zeolite can buffer soft water. Zeolite can remove certain

heavy metals from the water. Another property is its ability to remove

odours from the water. Indoor koi ponds can have a "fishy" smell.

Adding zeolite to the filter will eliminate these odours. Zeolite can be

used in ponds as ion-exchange medium for ammonia removal. Zeolite also

varies considerably in its adsorption capacity. In order to use zeolite

for ammonia removal, pond water must be pumped through the zeolite

medium at least once every two to three hours that is the same for

biologic removal.

For effective ion exchange by zeolite, continuous and extensive

mechanical filtration is necessary.

Caution must be exercised when using zeolite in the system and salt is

added. Salt is used to re-charge zeolite and adding salt to a system with

zeolite can result in ammonia being released back into the pond and

poisoning the koi.

Activated carbon

Usually used in granule form. Removes negative ions such as ozone,

chlorine and fluorides from the water. Heating to 900 o C can recharge it.

Very useful when used to filter mains water where chlorine and other

chemicals have been added to the water. It can be expensive and only

certain types of activated carbon remove ammonia and chloramines..KHA Program – Filtration Module 50

Water Changes (water changes out)

See page 47

UV Lights

UV or Ultra-Violet Lights are a type of light that has a specific band of

wavelengths primarily used for controlling algae. The bulbs used in ultra

violet systems are designed to produce a light of a specific wavelength

(around 254 nanometers). This frequency has a maximum take up of the

light by the DNA in the living organisms.

Ultra Violet (or UV) light has been used for disinfecting water since

about 1910. The effectiveness of the light depends on a number of

factors including bulb wattage, age, turbidity of the water, cleanliness,

the distance between the bulb and the organism, what the organism are,

as well as the duration and intensity of light that the organism is

exposed to.

The way UV works is similar to the things that happen when we sit out in

the sun. The UV light kills off the DNA in the cells causing them to die

As a rough guide water borne algae and bacteria require a dose rate of

15,000 - 30,000 mW-sec/cm2, whereas protozoa require doses in the

region of 45,000 mW-sec/cm2.

Disinfection rates differ in various papers and there is much conflicting

information. Methods used in the laboratory are often very different

from those in commercial aquaculture.

A UV light will only affect those organisms passing near it. It will not

have any effect on those organisms in the pond itself.

Vegetable (plant) Filters

Plants in streams and in filter chambers can be utilised to remove

certain substances from the water. Although plants do not remove

ammonia from the water they do remove some nitrite and nitrate. The

roots of plants that dangle in the water, such as water hyacinth, can

hold large colonies of both nitrifying and hetrotrophic bacteria.

Any planted area must be continually maintained to prevent the root

system clogging up and cutting off the passing water from lower regions.

These regions will be become anaerobic and poison the system

Streams as Filters

Streams can be used as biological filters. The bed of a stream can be

laid with gravel or stone. As the water passes over this bed nitrifying

bacteria will grow.

Streams as filters must be shallow to prevent anaerobic bacteria.KHA Program – Filtration Module 51

forming in the lower regions of the gravel bed. The gravel or stone bed

will be a wonderful trap for organic material. In other words this bed

can clog up easily over time.

Cleaning the stream regularly of organic material is critical to its

success.

Foam Fractionation

Some times called foam floatation and protein skimming

This is a process that removes organic matter and fine solids from

water in the form of a foam that is generated in a device.

A foam fractionator consists of three parts, a vessel (usually a column)

through which the water flows either up or down, a bubble source ( such

as a diffuser or venturi) and a foam collection point. Foam fractionators

do not work nearly as well in fresh water as in marine environments.

Fresh water implementations are much more difficult to control.

The particulates that foam fractionation removes from the water are

known as surfactants, and are comprised mainly of organic compounds

(proteins). These compounds have one end that is attracted to water

molecules (polar) and one end that repels water molecules (dipolar). As

the bubbles rise through the column, the molecules collect around the

bubble surface with the dipolar ends in contact with the air and the

polar ends pointing out into the water. The molecules are therefore

adsorbed into the surface of the bubble. Once the bubbles reach the

water surface, the particles in the bubble surface prevent it from

bursting and as more bubbles collect behind it, foam is formed.

This foam rises steadily out of the water as more and more bubbles

build up behind. The diameter of the column is gradually restricted at

the foam outlet, which increases the velocity of the foam, it is then fed

away from the column and sent to waste. The increase in velocity is

important as it reduces the amount of time that the bubbles have to

stay in tact for, before they are removed from the column. The amount

of foam produced is a result of the air flow rate, the amount of

surfactants in the water, and the time taken for the foam to be

removed.

Foam fractionators are often used in recirculating systems to remove

some of the fine solids and reduce the loading on biological filters.

Foam fractionation can be observed on a daily basis in the pond. Ponds

with high organic loads or changing water quality often have a foam

developing at the base of a water fall – where the air bubbles attract

the DOC or dissolved organic carbons..KHA Program – Filtration Module 52

CONTINUUM – Koi Ponds are often treated for parasites and

diseases. This practice is dangerous and we discuss why in

Chapter 8: Effects of Chemicals and Medications on Filtration …

CHAPTER 8: EFFECTS OF CHEMICALS & MEDICATIONS

ON FILTERS

Effects of Various Chemicals and Medications on Filters

Koi Health Advisors should perhaps understand that there is no such

thing as koi medications. The vast majority of the substances we

administer to the koi and the vast majority of substances we add to the

pond water are poisons administered in limited dosages. These are

radical perceptions, yes, however virtually any medication or chemical

will disrupt the biological action in the bioconverter and may even kill

the koi if the dosage is high enough.

A simple mistake of having the decimal point a single digit in the wrong

place will increase the dosage by 10 times the recommended amount.

The wrong calculation of the pond volume can result in the dosage being

completely wrong and disaster will follow.

Different medications and different chemicals will disrupt the

functioning of the bioconverter to a greater or lesser degree –

depending on the type of chemical used and the dosage at which it is

administered.

Any substance that kills bacteria will very likely be harmful to the

bacteria in the bioconverters. This would include antibiotics and

oxidizing agents, e.g., tetracycline and potassium permanganate..KHA Program – Filtration Module 53

CONTINUUM – We need to develop an ability to analyse problems

in Koi Ponds. Therefore we conclude with. Chapter 9: Developing

and Eye for Problems Associated with Filtration …………………..

CHAPTER 9: DEVELOPING AN EYE FOR PROBLEMS

ASSOCIATED WITH FILTRATION

Message to Koi Health Advisors.

This part of the filtration module could have become a book on its own.

However we have decided to take a different path by using this section

to build a reference section together. Actually the case histories we

deal with as a group during the duration of this course will be discussed

and resolutions sought. Once we have solved the problem we can publish

the data as a case number without becoming personal. We will cross

reference cases for easy access.

In this way candidates will write this section together, based on their

experiences.

I believe this will be more practical and useful to candidates on the

present course and in the future.

Chris Neaves.KHA Program – Filtration Module 54

We will start with two real life case studies to get the ball rolling:

Case #1

History

A moderately experienced but enthusiastic hobbyist set up a quarantine

tank using a 500 gallon PVC show tank, a 35 gallon plastic trash can with

OC foam as a prefilter/bioconverter combo and a 65 gallon plastic

barrel with OC foam as a bioconverter. The units were joined in series.

The hobbyist overloaded the tank and did not watch the water

parameters closely. Eventually and upon observing distressed fish in the

tank, the hobbyist tested for ammonia and found very high levels. At

this point the hobbyist emptied 50% water from the tank and refilled

the tank from his pond believing that the ‘aged’ water would be better

for the distressed fish.

The Problem

The fish went immediately into worse distress with one fish expiring

before the hobbyist realized what was happening.

Testing later showed the pond water was at a pH of over 8 with a T.A.

of about 150 ppm while the tank was somewhere below 6 with very little

T.A.

Questions - Case #1

What went wrong with ‘the fix’ and what should the hobbyist have done

and in what sequence?

Analysis & Solutions

Case #2

History

A koi enthusiast has a pond of 13200 gallons. He has 55 large koi of high

quality ranging from 19 inches to 31 inches in size. Several are show

winners. He has a sophisticated filtration system with 4 vortex tanks in

sequence. The bottom drains bring the water into the first tank. The

vortex action settles out much of the solids. The water then passes to

the next tank that has Japanese matting as a biological medium. This is.KHA Program – Filtration Module 55

repeated in the third and fourth tank.

The water is drawn off the fourth vortex tank by a swimming pool pump

with a capacity of 6000 gallons per hour. The water is then pumped

through a single 30 inch sand filter to polish the water and is returned

to the pond via three inlets situated 12 inches below the water line.

The Problem – Case # 2

The fish are sluggish and are reluctant to feed. Some are degenerating

in colour. One or two lie continuously on the bottom

Questions - Case # 2

What is the problem or possible problems and how can they be

rectified?

Analysis & Solutions – Case # 2.KHA Program – Filtration Module 56

INDEX

activated carbon, 16, 49

algae, 6, 9, 11, 13, 18, 19, 21, 32, 35, 46,

50

ambient ammonia, 24

ammonia, 9, 11, 12, 14, 16, 18, 20, 21, 24,

37, 38, 40, 42, 44, 48, 49

anaerobic bacteria, 16, 36

antibiotics, 44

bacteria

bacterial growth & pH, 14

bacteria in the bioconverter, 28

bioconverter, 6, 8

bioconverters, 38

mature bioconverters, 28

starting up bioconverters, 39

biological oxygen demand, 39

bottom drain, 22, 46

placement, 22

brushes, 27, 33

carbon dioxide, 6, 7, 18, 20, 38

chamber surface area, 43

chemolithotrophs, 18

chloramines, 48

chlorine, 48

circulation, 25

clay media, 27

deep filter beds, 31

discharge box, 22, 34, 46

filter media, 28

various filter media materials, 29

filters

frequency of cleaning, 47

filtration, 6, 7, 8, 15, 16, 22, 25, 29, 32,

45

floating bead bioconverter, 41

flow rate, 8, 17, 20, 21, 23, 24, 25, 31,

35, 44, 51

through bioconverters, 23

flow rates, 24

advantages of faster flow rates, 25

and ammonia levels, 24

and oxygen levels, 24

importance of, 21

flow rates & ammonia, 24

fluidisation, 41

fluidized bed filters, 41

foam floatation, 17

foam fractionators, 51

free nitrogen, 37

gravel, 27, 29, 33, 35, 41, 43, 51

heavy metals

removal from the water, 49

heterotrophic, 39

heterotrophic bacteria, 17, 28, 39

hydraulic load, 30

hydrogen sulphide, 25, 30, 46

in pond filters, 41

lava rock, 29

marble chips, 27

mature filters, 23

mechanical filters, 32

media, 16, 17, 19, 20, 23, 27, 29, 30, 31,

33, 34, 40, 41, 44, 47

surface area, 29

media lay-out, 30

medication

effects on the pond, 52

metabolism, 6, 13, 14, 15, 16.KHA Program – Filtration Module 57

nitrate, 37

nitrifying bacteria, 8, 9, 11, 14, 20, 23,

27, 29, 38, 39, 40, 42, 44

nitrite, 37

nitrobacter, 38

nitrosomonas, 38, 39

nitrospira bacteria, 38

nitrous oxide, 16, 37

odours

removing odours from the pond, 49

organic material, 32

oxygen, 6, 7, 8, 9, 11, 12, 13, 14, 15, 18,

20, 21, 24, 25, 30, 31, 36, 38, 39

dissolving oxygen into water, 25

oyster shells, 27

parallel, 17, 35, 36, 44

pH, 11, 12, 14, 15, 20, 37, 38

and bacteria, 14

and koi, 11

pipes

gravity fed pipes, 22

plastic material, 27, 33

plastic media, 27

polyurethane foam, 27, 33

potassium permanganate, 52

remove solids, 37

removeing solids, 6

removing solids, 25

sand filters, 34, 35, 36

screens, 33

seeding the bioconverter, 40

sequence, 17, 54

settled solids, 18, 25

settling chambers, 34

shutting down filters, 44

specific flow rate, 17

sponge, 33

stand pipes, 46

stone, 43

streams, 51

surface area, 19, 25

of the media, 19

surface area of the bioconverter, 43

surface area of the media, 28

suspended solids, 18

temperature, 10, 12, 13, 14, 15, 37

total surface area, 29

trickle bioconverter, 40

turnover rate, 25

of the whole pond, 23

turn-over rate, 20

ultra-violet lights, 50

vegetable filters, 50

venturies, 8, 13, 21

vortex, 40

water

bottom water, 22

hardness, 49

water changes, 47

zeolite, 16, 27, 49

 

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