KOI POND CONCEPTS:THE BASICS AND THE IDEAL POND

By Galen Hansen, M.D.
Reprinted from KOI USA

Introduction
This article is a compiation of many koi experts' and enthusiasts' views, with an intermingling of my own views. . Besides collecting data from amny issues of KOI USA and Rinko Magazines, there is reference to Tetra's Koi Encyclopedia and heavy emphasis on Grant Fujita's book. My main goal is to give the koi hobbyist the foundation of what both a Basic beginner's pond as well as an ideal pond should contain. Realizing that not everyone has the space, money, nor ambition to do all that is mentioned in my paper for the Ideal Pond. I at least try to emphasize those things that every koi pond should have to both minimize the maintenance and, even more importantly, to improve the health and quality of their koi.

All of we koi hobbyists have later on wished we had researched the necessities of a koi pond in more depth, or had done something differently the first time around. Do you know anybody in the koi hobby who has not made major changes in their pond or filter after a few years and could kick themselves for not listening to the more experienced hobbyist originally? This is particularly true in not making the pond large and deep enough initially. I can say without hesitation that I am very guilty of this.

It is for these reasons that I have tried to summarize the literature, as well as the ideas of many experienced koi hobbyists. Even some of what I propose may find disagreement with other koi enthusiasts. But this is what makes us all grow in the hobby! This paper should. how-ever, provide you with a good starting point on areas which you may want to consider initially or changing.

The Basic Pond

Many beginners in the koi hobby begin by digging a hole in the ground, lining it with concrete (or a liner), put water in it and gradually fill it up with koi. Well, this may work for a backyard goldfish pond but it is inadequate for a koi pond. There are even koi hobbyists who had their beginnings with koi in an aquarium. However, they soon learn that such a small environment limits their growth and that koi are meant to be viewed from the top and are rather unattractive from the side. Some may disagree. saying they have a small back yard pond; only 1 to 1 '/2 feet deep, 3 by 5 feet in size and have a couple of koi in it which have lived for years. Well, this may be true; but if you hang around with the same koi hobbyists that I do. a couple of koi will never suffice, and the five inch koi you originally bought has grown into a large koi. The biological load of your new koi or growing koi will result in overcrowding and an increased load of wastes and ammonia which deteriorates the water quality. Buying new koi will also bring in diseases which your old koi may not be immune to. So now we have a small overcrowded pond with some diseased koi and our enthusiasm quickly wanes.

Next we learn that there are 14 differnt kinds(classes) of koi with some subclasses, and that no two are alike, yet we are cornpromised with this small backyard pond. The water now turns to pea-soup green; there is no means of cleaning the pond except by draining it and then worrying about the chloramines in fresh water that will kill the fish if it is put in all at once. So what can we do to this small pond so that we can:

1. have easy maintenance. i.e.. be self-cleaning.
2. keep the water both clear and clean, both for viewing of koi and for water quality,
3. enable us to buy more koi,
4. and keep them healthy and in superb condition so that they do not lose their color or luster?

The answer is that every koi pond, unlike a goldfish pond. needs:

I. an oxygen source. i.e..a waterfall,
2. a purification system. i.e., a biological filter.

BIOLOGICAL FILTER
A follow-up paper is forthcoming on the "Ideal Biological Filter." For this reason, suffice it to simply explain now the purpose of Biological Filter, the Purification System. The actual design will be discussed in the next paper.

Unlike a swimming pool filter, which is to keep the water clear and clean, it is the chlorine added to the swimming pool which keeps the algae from growing on the sides of the pool and is really responsible for the clear water. In a koi pond, we cannot use chlorine and we want the fine velvet coating of algae to grow on the sides of the pond. In fact, if algae does not grow on the pond sides then there is a major water quality problem. Your koi nibble on this algae. providing nutrients. giving them their luster and color. We also want the water to be clear so that we can always see our koi, therefore something other than cholrine must keep out the unicellular algae (causes pea-soup water) and the long stringy algae. These are the purposes of the Biological Filter.

Likewise, just because the water is clear does not mean that it is healthy for the koi. In fact, the ideal water is clear with a slight greenish tint, as well as being odorless and tasteless. Your koi produce wastes:

(1) ammonia from their urine, which diffuses, yet the water remains clear and it becomes toxic to the koi as it builds up:
(2) solid wastes which also add more ammonia, plus toxic hydrogen sulfide, methane gas, etc. and it clouds up the water.

Other debris. as dirt,leaves, and uneaten food adds to the accumulation of toxins to the water quality.

To purify all of these wastes is the purpose of the Biological Filter. It contains a biological material for aerobic bacteria to grow upon. These bacteria metabolize and rid the pond of the ammonia and wastes. Such a biological material in the 1980s would have been pea gravel or volcanic rock. Nowadays, however, many synthetic materials are being used (brushes, foam, mattresses, bioballs. etc.). The major requirement being that it contain the most surface area to house the maximum amount of good bacteria (aerobic). As stated. these large numbers of good bacteria rid the water of wastes and keep it clean and clear.

Important points of a Biological Filter:

1. Ideal to be outside the pond. i.e., better to not have the koi swimming in their own wastes.
2. Should have at least 1/3 the surface area of the pond.
3. Need a means of cleaning (backwashing and/or having bottom settlement compartments to flush out accumulated debris).
4. According to some experts, needs twice the amount of oxygen as the koi in the pond to keep the ggod aerobic bacteria and to keep out the bad anaerobic bacteria.

And remember, just because the pond water is clear does not mean that it is healthy water.

OXYGEN SOURCE:(WATERFALL)
The oxygen source comes from water movement. A waterfall is the most efficient and appealing supplier of oxygen. A fountain also works, as does any method of exposing water to the air. However, the water surface may be so disturbed by a fountain that one cannot view the koi. The koi must have oxygen. and as mentioned, the biological filter needs even twice the amount that the koi do. They also must have oxygen 24 hours a day. When I started in koi, I put my pump running the waterfall on a timer so that it would shut off at night. Why run the waterfall at night when it was dark and you could not even see it? Well, the oxygen level drops off when there is less sunlight and the algae present always consumes oxygen at night (produces it in the daytime). Thus, it is even more important to run the waterfall at night than during the day. Of course. the correct answer is to provide oxygen for your koi and your filter 24 hours a day. A power outage of more than 12 hours will result in your koi coming to the surface gasping for oxygen and eventually dying.

What about plants providing oxygen at night? Wrong again! Plants (water lilies, hyacinths, etc.) provide oxygen during the day when there is sunlight but use up oxygen at night. Thus, plants are (1) competing with koi for oxygen at night and (2) causing stress to the koi by affecting more rapid pH changes between day and night. Plants utilize carbon dioxide during the day butexcrete it during the night. Do not get me wrong, though. One can still have a nice koi pond with an acceptable balance of koi and water plants. Most hardcore koi enthusiasts do not have plants in their ponds however, because:

1. the koi hide under them
2. they encourage the koi to spawn and lay eggs that attach to them
3. as the koi grow, they begin eating the plants. What are the ideal requirements of a waterfall? The longer and broader the waterfall, the greater the aeration. The larger the area of water surface broken up by the waterfall entering the pond, the better the aereation. The entrance area of the waterfall into the pond needs to be a direct drop of a few inches otherwise the water will shoot directly across the surface and:
- a. will not mix oxygen into the depths, and
- b. will roughen the water surface thereby obstructing the viewing of the koi.
4. The waterfall must be run 24 hours a day.

Sloped Bottom to a Bottom Drain
The last need for the basic pond is to have a bottom drain with a valve on it. The bottom should slope down to the drain so that all the debris does not accumulate in the "dead areas" in the pond. The slope should be at least 20 degrees. If you do not put a bottom drain in the pond you will wish you had. The same if you keep the pond bottom flat, as you will have to constantly clean the pond. Without the bottom drain. you can still drain your pond with a sump pump. Thus it is not crucial to have a drain and sloping bottom, but you will greatly add to your work.

The Ideal Pond

Limitations on space and money are two major variables in constructing a pond. Of course, the more space and money the nicer the pond. In this section of the paper. I want to list all of the ideal items or recommendations to have a perfect pond. Of course, very few of us are going to be able or to even want to do everything which I have listed. My purpose, nevertheless is to include everything which would make an ideal pond and let the reader decide where to draw the line. The beginner will in no stretch of the imagination think that much of this is necessary. But the advanced koi keeper will wish he had done all of this and perhaps then some. Perhaps somewhere between the basic pond and the ideal pond would be your preference.

The following three points must be emphasized:

1. A koi pond is for koi, not for people
- a. The pond may be pleasing to the eye but may not accommodate koi
- b. A koi (carp family) is environmentally adapted to running water, not to a stagnant pond
2. Never build a pond without viewing other people's ponds, talking to koi enthusiasts, or going to koi club meetings.
3. If you have a professional build your pond, be a skeptic and ask questions, a swimming pool builder or even a pond builder may not understand the needs for koi.

Location
The main point is to put the koi pond where you can enjoy it to the maximum, the nearer the house the better. It is very important to visit your pond at least twice a day without exception. But the koi pond should not be:

1. where it is accessible to the public and may be vandalized:
2. under a tree which deposits debris into the pond:
3. where surrounding run-off water will drain into the pond.

ABOVE GROUND OR IN GROUND?
Koi are viewed from above, as all of their beautiful color and pattern, which make koi distinct from any other fish, is on their tops. A koi viewed from the side, as in an aquarium, is not very attractive. That same koi viewed from above may be outstanding. Thus, a koi pond ideally needs to be in the ground, so one may look down upon it.

PROVIDING FOR SURROUNDING DRAINAGE
Drainage of surrounding water may be a problem. Fertilizer from a surrounding lawn can easily wash into a pond during a rainstorm, this will kill your koi. So there must be an effort to keep drainage going away from the pond, either by

(1) sloping the surrounding ground away from the pond.
(2) adding a two to three inch lip or pond edge above ground level which is watertight.

THE PURIFICATION SYSTEM
As discussed under the basic pond. the purification system is the biological filter. The most important emphasis is that its size must be adequate. To reiterate, the surface area of the biological filter should be at least one third that of the surface area of the pond. Taking this to the point of being ridiculous, ideal would be that the filter should be the same size as the pond! Do I make my point? Everyone initially makes the error of having too small of a filter. A small filter will be inadequate for maintaining the water quality and your once gorgeous koi will deteriorate: you will get discouraged and want to get out of the hobby.

OXYGEN SOURCE Again, as in the basic pond. the more the water-flow, the greater the oxygenation of the water. A waterfall is the simplest and most attractive source of this oxygenation. (See the previous discussion on Basic Pond.)

SIZE
Ideally, the size of a koi pond should be as large as one can spare in the space provided. Without exception, everyone, after two to three years, finds the size of their pond inadequate. I repeat, without exception the first pond is not large enough!
Three points to remember:

1. Do not make it so large that cleaning the pond. catching the koi, or viewing the koi are impractical.
2. Leave room for the biological filter. At least one quarter of the space should be for the filter, even though probably hidden from view.
3. Put the pond in an ideal location for viewing, i.e., not so far from the house that you cannot keep an eye on it. Also, not in the front yard where it can be easily vandalized.

DEPTH
It is ideal to have the pond depth at least six feet at its deepest area. If this is not possible, at least go deeper than three feet. The major reason for depth is the health of your koi. There is less temperature variance during extremes in hot and cold weather, especially between day and night. Koi in deeper ponds get much more growth and bulk. Koi are physically comfortable in deep water. Shallow ponds also invite predators, i.e., blue herons, which simply walk in and spear the koi. There is no logical reason to have different levels of depth, as the koi should be able to swim unimpeded. My pond has a shallow swimway connecting two ponds: the koi tend to scrape their anal fins which becomes an entry point for aeromonas.

Shape of Pond
A koi pond may be any shape which one wishes to design. The most important limiting factor is that there should always be water movement in every portion of the pond. That is, there should be no dead areas! These are areas where there is static water - great breeding grounds for serious disease-causing bacteria. Dead areas are also areas where debris collects.

Thus, in your design plan, always be sure that the water is moving in all areas of the pond, from the waterfall at one end of the pond to the oulet drain and skimmer at the other end.

Corners & the Bottom
The junction of the sides, or corners, of the pond should not be square, but should be rounded. This prevents debris from collecting in these "dead areas." Also, the bottom should never be flat. How often are you going to walk in your a koi pond? The bottom needs to slope 20 to 40 degrees toward the bottom drains, so that the wastes collect in an underlying sump or distal settlement tank.

NO SHARP OBJECTS
Please, never, never put anything sharp in the pond on which your beloved koi may injure themselves. Sure, nice rocks jutting out of the pond may look attractive, but you will soon see many cuts, laceration and bruises on the kol. This includes no sharp rocks around the edge of the pond which the koi may jump out of the water and strike. Any pipes which end in the pond water will also be a hazard to the koi.

All Pipes Need Valves
A good rule of thumb is to put a valve on every pipe in the pond. This may seem excessive, but you may later wish you had done so. One needs the ability to isolate every pipe in case of a break or malfunction. In fact. major drain pipes could use two valves in case one fails. When you design your pond, lay out all the pipes before ever proceeding, especially before cementing. Plan where to put each valve.

PIPE FOR ADDING WATER
A one half to three quarter inch pipe from a water source emptying at the top of the waterfall, hidden from view, is an ideal convenient way to add water to your pond. Flow must be controlled by valves, ideally two of them: one at the beginning of the watersource and the other at the waterfall end. This is superior to adding water with a garden hose and is less likely to result in forgetful overfilling of the pond, if left at a slow trickle. Adding fresh water in a slow trickle is tolerated by the koi. They adjust to such a trickle of water and the water first flowing over the rocks of the stram or waterfall helps to remove the chlorine by exposing it to air.

Prior to water being tainted with chlorine/chloramine, or if one is blessed with well water, it used to be recommended to have the daily ratio of fresh water to filtered to be 15 to 20% fresh - 80 to 85% filtered. Japanese breeders advise the following:

1. to hasten the growth of the koi increase fresh water to 25%;
2. for better coloring, decrease fresh water to 10%., that is used or filtered water is better.

SKIMMER
Every pond needs a means of removing surface debris. There are two set-ups which may accomplish this:

1. A standard swimming pool skimmer with a trap So that small koi do not get sucked in.
2. Or a four inch pipe vertically, whose edge is at the water surface in the pond. In either case, both need to feed into the waterpipe that takes the pond water to the settlement tank (or to the filter). As in all other pipes, it needs to have a valve in order to turn it off when the need arises.

OVERFLOW
An overflow pipe draining out into the garden. slightly higher than the skimmer level, keeps the pond water from rising to the edge of the pond and carrying the fish over the sides. One can use either a vertical standpipe or a horizontal pipe through the side of the edge of the pond, placed at the optimum height of the water level. As stated previously, this level should be six inches from the top of the pond. A grid must be placed over the horizontal pipe to avoid losing small koi through it.

Bottom Drain
As in a basic pond, every koi pond should have a bottom drain. Such a drain needs to be able to function in one or all of the following three capacities:

1. Simply a bottom drain with a grate over it so that one can drain the bottom water (dirtiest water) out of the pond when one desires.
2. Continuously take the pond water to the filter, particularly if it goes through the settlement tanks first.
3. Or in the case where the water going to the filter is being removed from the pond one to two feet above the pond bottom, then a sump should be beneath the bottom drain so that every morning (and evening) sump out the bottom water which contains ammonia and wastes.

Ideally, all three possibilities in one pond is best.

The following is recommended for a bottom drain:

1. Put at the opposite end of the pond from the water inlet. i.e., the waterfall, so that all debris flows toward the bottom drain.
2. Drains must be at the deepest part of the pond with the bottom sloping toward it at 20 to 40 degrees.
3. The minimum number of bottom drains: every 10 feet apart. Maximum would be every six feet apart.
4. Each drain should have a separate drain pipe, otherwise if one connects two drains to a common outlet, the effective pulling suction power is cut in half for each individual bottom drain.
5. Outlet drain pipes should be no less than three inches in diameter.
6. Drain pipe covers should be a grate or a dome. The former can be purchased, made of PVC or iron. The latter can be made from cement, using a garbage can lid as a mold and putting four 1/2 inch feet on them.

WATER OUTLET: RETURNING TO FILTER
The optimum is to remove the solid wastes returning to the filter so that the biological filter is noe overburden and can work on removing the tiny partices and invisible wates, such as ammonia. The last thing you want is to have the pond act as a settlement tank and leave all the wastes, debris and ammonia at the bottom of the pond. So they must be removed from the pond but not taken directly to the functional part of the biological filter.

There are two alternatives on where in your pond to put the water outlets, taking the pond water back to the filter. Which you use depends on if you use a sump or a settlement tank, that is, how you rid your solid wastes:

1. If you return pond water directly to the filter without the benefit of a settlement tank, then the best place for the outlet exiting is from the bottom half or third of the pond. In this case one must have a sump under the bottom drain and sump out the debris and ammonia collected on the bottom daily. Better yet, sump off the bottom water twice daily. This water will be brown and smell of ammonia. Sump it out until it clears (at least 30 seconds). An added safety feature: If the outlet pipe breaks, the pond will not completely drain, since the pipe is one third the way from the pond bottom.
2. Better yet is to have a settlement tank or two or three. Thus, the water from the pond goes through these chambers so that the wastes settle out before they reach the biological filter. In this way, debris and ammonia never get a chance to sit on the bottom of your pond if built correctly. With settlement tanks, the outlet should be on the bottom of the pond. By the pond water going to the settlement tanks before going to the biological filters, both the koi and the biological filter have the cleanest water possible at all times.
To prevent accidental pond drainage, bring the pipe from the bottom drain up about two feet at right angles before leveling off again, then going to the settlement chambers. Now if there is a break in the system there will still be two feet of water in the pond. It is best to have the capability to filter off either bottom water or the middle water, so that you may do either or both. Bottom water returning to the filter is particularly best when the nitrifying bacteria of the biological filter is low, as when starting a pond or in the hot spring months.
SUMP
Every bottom drain should have a collecting chamber. i.e.. sump beneath it to collect all debris so it may be drained out every morning, if not also evening. In the case of the pond having settlement tanks before the biological filters, then these tanks also need sumps on their bottoms. Remember, your pond is the biggest settlement chamber that you have. A sump is a means of getting the wastes out of your pond before they get to your filter, thereby improving the water quality. Bottom water contains ammonia, fish wastes, uneaten food, dirt and leaves, all of which allow the bad anaerobic bacteria to grow in your pond and filter andcause disease.
Make the sump one to two feet in diameter out of concrete, funneled down to the drainpipe. It would be ideal to put two valves on each drainpipe to prevent accidental drainage of the pond. Likewise, as indicated above, the drainpipe should be brought up about two feet at right angles from the level of the bottom to prevent accidental drainage.
STANDPIPE CHAMBER
Another alternative set-up to allow drainage of bottom water yet prevent accidental drainage is the standpipe chamber. In this system, the drainpipe is taken to a chamber the same depth and level as the pond. A pipe is inserted over the drainpipe which comes into the standpipe chamber at right angles. This removable pipe rises to just above the height of the water in the pond. Simply by removing this pipe, with no valves involved, the bottom water from the pond floods into the much smaller standpipe chamber until it reaches the height of the pond (or until the vertical pipe is placed back onto the drainpipe). This acts as a sump which has a built-in safety factor preventing accidental drainage. Each bottom drain should go separately into the standpipe chamber, each with its own vertical removeable pipe. Then there should be a pipe which drains out this water to the surrounding garden after the vertical pipes are put back into place.
SETTLEMENT TANKS
These will be discussed in a future article on biological filters, as they are to be built outside of the pond. In fact, generally they are part of the filter, so that the pond water goes through them first to allow settling out of the solid wastes. Ideally, after the water goes through one to three settlement chambers, it then goes through a mechanical filter, and finally to the biological filters.
Each settlement chamber has three requirements:
- 1. The pond water must enter the settlement tanks near the middle but leave the chamber from near the top from the opposite side.
- 2. There must be a bevel to slow down the flow of the water to allow the solids to sink to the bottom.
- 3. Each settlement tank should have a v-sloped hottom with a bottom drain tomact as a sump, thereby flushed out every morning.
WATER JETS
When I built my second pond, something all addicted koi hobbyists do, I was talked out of water jets. A mistake! Here we are taking a fish whose natural habitat is a running stream, so we should do everything possi ble to simulate the natural state in our artificial conditions. With a water current provided by jets, the koi swim more, building up their strength, thereby improving their shape (conformation), their health, and their resistance to disease. It also minimizes dead areas, plus pushes debris toward the bottom drains.
These jets are in addition to the waterfall. To make a jet, T-off a one half to one inch flexible PVC pipe from the pipe returning filtered water to the waterfall, distal to the pump. Put in a valve to control the amount of flow on each pipe going to a jet. It is ideal to have at least two jets, one 18 inches deep and one elsewhere at a deeper level. A pond four feet deep or more should have a bottom jet. In the winter, when koi are inactive, shut off the deep water jets.
The jets need to be pointed in the same direction so that water current all flows in the same direction. The experts contend that ko all tend to swim counterclockwise. therefore this is the best direction to direct the jets. Coordinate this with the waterfall so that the two are not opposing each other. Now some say that the direction of the jets should be adjustable, so some of the time run them in an opposite or clockwise direction. The feeling being that koi swimming in the same direction always will begin to get lordosis, or curvature of the spine, if not alternated.
VENTURI VALVES
A venturi valve may be placed on one of these jets for the purpose of putting more oxygen in the water. A venturi valve is the same as a water jet with an air supply pipe to cause bubbles, as in a spa. So not only do you get a jet of water but also an added abundance of air providing more oxygen for your koi.
KEEPING KOI IN
Koi tend to jump at times. This is especially true when:
- 1. Koi are new
- 2. New koi are put in the pond in the evening
- 3. Koi have parasites
- 4. Water quality is poor irritating their exteriorsor gills.
We have all gone out in the morning and found a stiff koi on the lawn. Koi can be revived even after out of the water more than an hour. I have revived koi merely by working their gills under the waterfall after finding them looking very dead, stiff and dry.
The following encourages koi to stay in the pond even if they do jump:
- 1. Keep the water level six inches down from the top of the pond edge.
- 2. Do not slope the sides of the pond but have them go straight down for at least the first two feet of depth. This prevents a running start by the koi.
- 3. Some even put a lip overlapping the edge of the pond so that if the koi do zoom along the sides and jump, they will hit the lip and stay in the pond.
- 4. If koi do jump out, they do try to flop back in.
Thus, the two factors which I recommended to keep drainage water out would act to prevent the koi from jumping back into the pond. So, you want to minimize the elevation of the pond edge, keeping the surrounding water out but still allowing an errant koi to flop back into the pond. Likewise. minimize the slop