HOW TO BUILD AND MAINTAIN A PROPER KOI POND

By Tom Burton

CONTENTS
 Introduction
Siting
Size
Depth
Bottom drains
Filtration
Pond construction
Heating
Routine maintenance
Catching fish

A koi pond is a purpose built habitat for those lovely fish we call “Living Jewels” and as such, differs from any other garden water feature. To introduce koi into other types of water features is usually a disaster waiting to happen and though one can get away with it for awhile, the end result is predictable. So, instead of doing what so many do, that is dig a hole, throw in a liner, add water and a few fish, and call it a koi pond, we want to help to get it right the first time. You only need to do it right once but you can get it wrong over and over.

This chapter will address building a koi pond with a liner but the only difference between a liner pond and any other is what’s used to contain the water. All other technical aspects are the same; bottom drains gravity feeding to a filtration system then to a biological processing station before being returned to the pond by recirculating pumps. But before attempting to build, read and heed the advice in this excerpt from the Mid-Atlantic Koi Club publication, From the Pages of MAKC News:

“It seems that the more people that see koi, the more people there are that want to own one (or 10 or 50). But to make the transition from dream to dream pond, there’s an awful lot of information that must be read/seen/heard and assimilated before one has even a chance of success. So to preclude those would-be koi keepers from putting the carp before the horse, here’s a logical approach to what can be and in most cases is, a most rewarding and fascinating hobby.

“The first rule is:

-- DON’T BUY ANY FISH YET!!!--

“Not only join a club but actively participate in all of its activities that you can make time for. Listen to any and all who will respond to your questions. You’ll get plenty of conflicting stories but after awhile you’ll be able to sift through the chaff and can start to formulate a well founded base from which to do your planning.

“Go see as many ponds as you possibly can, all the while asking questions and storing the data for your future use. After awhile you’ll have some ideas on what your budget, real estate and imagination can handle so retrace your steps (or continue your search) until you find the THE pond, up and running, tried and true, that comes closest to what you think you want. Talk extensively to that pond keeper and find out from the beginning how he made it work and what were the mistakes and pitfalls along the way (that you can now avoid).”

An ideal way to have the beauty of a water garden AND the distinct pleasure of a koi pond is to have both! - a lovely water garden tippling off into a koi pond. The plants can’t be disturbed (or eaten) by the fish because the fish can’t get to them and the fish can be viewed in all their glory, unfettered by pots and plants.

Perhaps one the most difficult but truly critical aspects of building a koi pond is where we put it. The whole point behind doing this in the first place is to be able to see it and enjoy it so if we put it off somewhere in the “back 40” we might as well save ourselves the trouble. Ideally, the pond will sit where we can see it from the house all year ‘round. We may need to remove an old concrete patio or demolish or remodel a deck or even transplant or remove some existing plants or trees, but it will be worth it in the long run. Deciding just where it will go and what it might look like will take some imagination but that can be helped by using a rope or garden hose or even spreading lime to outline the pond’s perimeter on the ground. Then, viewing it over several days from many angles from rooms in the house as well as from the surrounding property will help in deciding the ideal spot. And finally, while we’re at it, we may decide to replace some windows with a larger expanse of glass so as to incorporate the outdoors with the indoor living space. This is an excellent way to heighten the enjoyment, particularly if the pond is close enough to the house that we can walk to that window and actually see into the pond and watch the kaleidoscope of colors as the fish swim in ever changing patterns.

Once the “where” is decided, we need to determine size and depth.

An ideal pond for the average hobbyist is between 23 and 25 feet long by 12 to 13 feet wide and 3 to 4 feet deep. (The 1% or less of koi hobbyists who want to grow jumbo koi or keep fish primarily to compete in shows with, will want much deeper ponds of 6 to 8 feet). This size pond can accommodate 15 to 20 mature fish (24 to 28 inches) giving them plenty of room to exercise and, will not look overstocked and crowded. Here’s how we calculate the volume of water in this pond: Length X width X depth = cubic feet X 7.5 gallons per cubic foot = volume in gallons. So, 25 X13 X 3 X 7.5 = 7312 gallons. However, this is only an approximate figure as the pond will not normally be a perfect rectangle and the shape may be more freeform. We will only know the exact volume of pond and filtration system upon filling the feature and metering the input. And it’s extremely important to know the exact volume.

Keeping the width of the pond to less than 13 feet is so that when we have to catch a fish, for whatever reason (and there will be reasons), we need to be able to extend the net from one side to the other and any net and handle longer than about 12 feet is quite unmanageable. (See section on catching fish).

They’ve just discovered an eleventh stone tablet somehow missed by Moses. The inscription reads, THOU SHALT NOT BUILD A KOI POND WITHOUT A PROPER BOTTOM DRAIN. Imagine that. Even then they knew. The ideal set-up is to have the drain(s) CONTINUOUSLY gravity feeding to the filter system(s). Why gravity feeding? So the big stuff stays as much intact as possible as it enters and settles in the first phase of the filtration system, appropriately called the settling chamber. Why continuously feeding? Because crud lying static in the bottom of the pond and in drain pipes waiting for someone to purge it, quickly becomes anaerobic (lack of oxygen), starts producing that sulfuric or rotten egg smell, and poses a dire threat to the health and well-being of our treasured friends. This becomes even more acute during the winter if the filter system is shut down. Why? Follow this line of reasoning: If the water is not being re-circulated and stands relatively still, where is the worst water in the pond? AT THE BOTTOM. Where do fish stay in the winter? AT THE BOTTOM. If we don’t run our systems we force the fish to live in their own, continually worsening sewer. No wonder so many folks dread deadly springtime. AND, to absolutely compound matters, starting up from scratch each spring means all the pain and agony of “ New Pond Syndrome” every year. Ugh!! They say it takes a couple years for a biological processing station to become mature and although arriving at that conclusion was not done scientifically, experience sure bears that out. And as the water warms and we start and then gradually increase feeding, the filter is ready to react on demand as opposed to going through the tenuous ammonia and nitrite cycles/spikes on its way to kicking in. One last thing: a minimum of four inch drain pipe from a drain similar to the one on page 32 of the Tetra Encyclopedia of Koi, is still the state of the art (though a new drain from the UK that incorporates aeration shows great promise as well). Even a four-inch pipe will need to be cleaned out from time-to-time after about the fourth or fifth year of use as crud grows on the walls and really slows down the flow.

They say that the key to keeping koi is water quality. Then the key to water quality is adequate and appropriate filtration.

Any filter system (and the emphasis is on system) should include the following four, essential elements:

In addition to selecting a site for the pond, you need to decide where the filter system will go. It can go most anywhere -out in the woods, around the corner of the house, maybe in the garage - but it should either be concealed or suitably camouflaged so as not to intrude in the beautiful setting you're making. The use of a surveyor's transit will come in handy to make sure the water level in the filter system will be the same as the pond. These can be rented at equipment rental places and this is critical to the efficiency of a gravity fed recirculating system.

The next step is to lay out the pond perimeter using powdered lime or a rope or hose to see what this thing is really going to look like in the spot you've chosen. Again, it’s probably good to leave this for a couple of days to see if that's what you really had envisioned. Then, start digging.

If you live in an area where ice might be a problem, slope the sides about 20 degrees so the ice can slide up as it expands instead of straight out (and through your liner). Dig out the trench for the 4" bottom drain pipe and run it all the way to where the rest of the filter system will go. If a straight shot is not possible, use 45-degree elbows to raise or turn the pipe rather than 90's. The fewer bends the better. Put the bottom drain and all the pipework in place to check all the measurements before gluing. It’s a good idea to cover the whole top of the drain to keep dirt out. If the drain is sitting on firm virgin clay/soil, there's no need to set it in concrete. The weight of the pond water will hold it steady.

Returns from the pump and filtration system to the pond are usually via a waterfall and a couple of through-the- liner bulkhead fittings that allow for the creation of a current by using directional "eyeball" (spa) fittings or 90 degree Fernco elbows with the clamps removed (so the fish don’t hurt themselves) and glued to the pipe out of the bulkhead. Don't be afraid of the through-the-liner returns. Just be sure to tamp the backfill around each pipe so they're in a solid setting. It usually takes two people to install them and only go arm's length down the side - one person holds the outside of the fitting outside the pond (male threaded) while the other tightens the nut that sandwiches the liner against the flange (female threaded) for a water-tight installation. A bit of aquarium-safe adhesive wouldn't hurt either.

You've already decided whether you're going to have a partially raised pond and what that structure will be made of and look like, or you know what type of stone you're going to use around the place. The rule here is to hide the liner and the plumbing. The water level should always be a little above the exposed liner inside the pond. This means that the liner must not only go under rocks placed around the edge of the pond, it must come up behind them as well. To accomplish this, a shelf an inch or two below the intended water line is in order (remember, you know where the water line is going to be because of the levels shot with the transit). Hiding that back edge or tip of liner can be accomplished by using overlapping rocks, plants, decking, you name it (see diagram). Here's where your imagination comes to play. Just don't let it show either inside the pond or out. Decide how the excavation at the top perimeter of the pond should be done to arrive at the look you intended. Its a good idea to steer clear of a necklace or swimming pool look except maybe for a partially raised pond.

Now's the time to check the dimensions of the pond again and calculate the size liner you're going to need. Length plus 4' plus (depth X2), and width plus 4' plus (depth X2). That 4' in each direction is to give you 2' overhang all around. Thus a pond 25 X 13 and 3' deep needs a piece of liner a minimum of 35 X 23 plus any for bog garden, streams or waterfalls. If the stones you're using are more than 18" wide, you will need to add liner accordingly. The rule of thumb is, if water is going to be there, there must be a covering of liner AND a lip at the back to contain it. Don't forget to include a planned stream or waterfall. They need to be lined as well and the water contained on the sides (with the liner hidden of course). One contiguous piece for everything, to include the water garden if that’s in the plan, makes it a lot easier but there is an EPDM bonding material that does well when applied properly. Or, there is an EPDM tape that will work if applied with care and correctly. There are some good diagrams and examples of perimeter treatment in the Tetra Encyclopedia of Koi and though this book is an excellent reference, it’s rather dated, particularly in filtration, so check with other folks before accepting the material as gospel. The fundamentals are all there but technology and new developments have passed it by.

Now the hole is perfect and its time to lay a padding for the EPDM. Old carpet works well, as does sand or carpet padding, almost anything that will give a bit of cushion and help the liner resist puncture from underneath. Once that's in place you're ready to lay the liner. And since its pretty heavy, fellow club members or friends are needed for this operation. One method is to lay the whole liner out and roll it up from the sides to the center lengthwise then tie it in a few places to facilitate carrying by you and your friends. Then march single file through the hole, placing the liner properly lengthwise, then roll it out from the center and up the sides. Another way is to get six people to hold it out over the hole then gradually let it drop into place. Once its in the proper position, smooth out the bottom over the hole for the bottom drain, mark the hole with a Magic Marker, then cut the hole in the liner as neatly as possible with a utility knife. Then apply a fish friendly (aquarium safe) adhesive/caulk between the liner and the bottom drain, then on the collar that will sandwich the liner and the bottom drain together. With the collar in place install the screws or whatever fasteners came with the drain trying to apply equal tightening all around. Wait for that to set-up according to the directions for the adhesive, then proceed to lay the liner so as to avoid as many folds and wrinkles as possible (this the major down side to using a liner - some folds and wrinkles can't be avoided and will harbor crud). This was my saddest day as I couldn't imagine getting that huge sheet of rubber to flatten out and look like anything - but of course it mainly did and once covered with algae, and with gorgeous fish swimming around I don't notice it anyway. As the pond slowly fills its possible to work even more wrinkles out as the weight of the water starts to work in your favor. Its not a good idea though, to stretch the wrinkles out by letting water act as air would in a balloon - this ends up thinning the liner. Some folks have filled their pond, left it sit for a few days, then pumped it out and started the wrinkle removing process again as they refilled. They say it helped. Also, the use of 6" EPDM tape can help flatten and seal major folds. The anti-vortex domed top for the drain should be set about 1 1/2" off the bottom.

Now to the filtration system. At this stage you should have the system all hooked up and in place or have all the necessary parts on hand. You've kept the water in the pond from running out the drainpipes by closing the knife valve for each. Look at the attached filter diagram as only one of many ways and means to arrive at the same end; good water quality. The filter system is the key to that and if we don't have good water quality, we can't keep koi (very long) - period. The system incorporates bottom drain to settling chamber to mechanical filtration to biological processing to pump to pond. It doesn't matter what the containers look like, or what their shape is as long as they hold water and don't lose their shape when filled. The settling chamber won't work if we feed it too fast. The mechanical filter won't work if all the water isn't forced to travel through the filtration media. Likewise, the biological processing station won't work if the water can go around the media you've selected as the home of the good guy bacteria. Water will seek the least line of resistance and all of your efforts will be for naught if it doesn't go THROUGH the media. Also, match the media to the type container. Brushes do well in round, or straight-sided square or rectangular containers. Ribbon type media goes in either as well. Ribbon material will try to sneak out purge drainpipes if you don't contain it (say in nylon drawstring laundry bags or by having a grate at the bottom of the container). However, these are just a few of the potentials for media so ask and look around. They are ones I've used successfully though.

Now we can start up the pump and test our recirculating, gravity fed system. The pump should obviously be outside the pond and move 2000 to 2400 GPH. It normally doesn't have to create much head or pressure as water falls should neither look nor sound like Niagara Falls. The effect should be soothing, not kinetic or frantic but that's a personal thing I guess. Most of the water being pumped will go to the through-the-liner returns to create the current we mentioned earlier. The fish love it and the crud is moved to the bottom drain where it belongs. There are several choices of pumps and any one that uses around 3 amps and is quiet will do just fine. Most have 1 1/2" input and output connections. If you're going to use 2" pipe from (and/or to) the pump, just use a 1 1/2" to 2" coupling. Installing a ball valve (Teflon ones are best) on the output side of the pump for complete control, and a flow meter that displays 20 to 80 GPM, are highly recommended.

You're up and running now and have used some type of dechlorinator to neutralize the chlorine in the water and are ready to add a few fish who will provide the food (ammonia) for the good guy bacteria to get started. Remember that our biological processing station is only RE-active and never PRO-active so it always has to catch up to any increased bio load (so we never want to add a lot of fish all at once).

The best way to take control of our koi's environment year ‘round is to install a pond heater (no, I don't mean one of those little horse trough electric heaters). I've heated for the past 10 years and found that the fish thrive and I get to watch their graceful kaleidoscope of color, even in the dead of winter in New Jersey. A ready made bolt-on heating system is put together by John Hadley, also here in New Jersey, which costs between 3 and 3500 dollars. www.ntponds.com/pondheatering.htm . Or, one can do the DIY routine with a boiler, expansion tank, stainless steel heat exchanger, circulating pump (Taco 11 or 12 works great), and aquastat to control the demand for the heater. This would end up costing in the neighborhood of 1800 to 2200 dollars.

Here's what a readymade looks like.

If the bottom of the pond has been sloped a bit to the bottom drains, most of the crud will make its way from the pond to the filtration system without any help from the koi keeper. The returns through the sides of the pond from the filtration system will produce a bit of a current and keep particulate suspended and headed for the bottom drains or skimmer. However, there are routine maintenance tasks that need to be carried out periodically.

Some folks have said I seem to have a knack for netting fish. Maybe so, as it seems to come very naturally. But when asked to describe my method (or write about it) it’s sort of like trying to tell somebody how to ride a bike or learn to drive; there’s no substitute for experience. However, to shorten the learning process, here’s my methodology, for whatever it’s worth.

A 32” net is a “must” no matter what size fish you’re going after. The length of the handle depends upon the size of your pond, your strength (you’d be surprised how heavy and cumbersome that thing becomes with over a five foot handle), and whether or not you’ve got a “herder” to help keep the “target” fish in your reach. By the way, the herder never attempts to catch the fish.

I keep total concentration on the target fish, and the position of my net, all the while segre­gating the target. Don’t get distracted. Move very slowly. Don’t stress the other guys either. Let’s keep everybody cool and calm.

Start advancing on the target from the bottom of the pond. You want him to rise toward the surface (it would do you no good to have him in the net at four feet - he’d just swim away as you started your ascent.)

Once near the surface, the net should be moved under the fish and slowly raised to the surface with the fish “free” in the water in the net. NEVER lift a fish out of the water with a net as you may injure a scale or fin inviting a bacterial invasion in the broken mucus immune system.

At your side you have a large pan, such as we use at shows, which you can now, after having brought the fish hand-over-hand closer to you, dip into the net and allow the target to gently enter. Or you could use a sock net for the transfer but - NEVER lift a fish out of the water in the large net as it’s very likely to cause damage to fins or scales.

Sounds easy doesn’t it?

A couple other “nevers”:

If the fish darts past your net or jumps out of it, never give chase. Just start the process over again. Never stab the net at a fleeing fish. Suppose you nailed it to the side of the pond. That’s like taking a block from a Dallas Cowboy - survivable, but sometimes bringing injury and always bringing discomfort.

The old saw about “If at first you don’t succeed” comes to mind about now. Practice. And in the meantime, happy hunting.

*********************************

Biography: Tom Burton has been active on the Mid-Atlantic Koi Club Advisory Board, was ‘92 Koi Person of the Year, Northern Chapter VP for many years, and following training at the University of Georgia’s fish-vet course, founded MAKC’s Health Hot Line, now featured in the Mid-Atlantic Koi magazine. A frequent speaker on the subject of pond building, and a sought out pond building consultant, he has been well received at the International Water Lily Symposium, Longwood Gardens, the New York Botanical Gardens and Hofstra University as well as a guest speaker at Canadian events.

Tom is a retired military officer and though often called upon to consult or be offered employment within the Koi community, he has successfully retained his dedication to the hobby by remaining a pure volunteer. He is the second most published author in the well-received book From the Pages of MAKC News and is renowned for his design and building of one of the most admired ponds and gardens in the country.