Filtration

KHA Training Program

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

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

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

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

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 50ºF / 10ºC),

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.

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

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

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.

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 40ºF (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 35ºF. 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

- 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

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

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

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

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,

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

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

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.

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.

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

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

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

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

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

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

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.

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

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

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

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