Koi Pond Basics

The Beginning

Just about the most unnatural thing I can think of is a pond full of beautiful Koi, sitting in the back yard. Make it as natural *looking* as you can, if that's your goal, but don't kid yourself, there's very little that's "natural" about it.

Mother Nature seems to have a "thing" about brightly colored fish, at least in freshwater ponds in the U.S. Under Her control, the fish will camouflage to the point of invisibility, to escape being eaten by the many predators that frequent Her ponds. And she doesn't go out of Her way to keep very many fish of any size in Her ponds of 1,000 to 50,000 gallons, either. Increase the stocking level in one of Mother Nature's ponds and She will adjust it right back down, in short order.

If you think of your pond as being "natural," shut off your pumps, shut down your biofilter, remove the airs stones, stop all feeding, and wait. Mother Nature will soon step in and "adjust" it to Her liking. Her methods are, by my standards anyway, brutal.

I'm going to lay out for you what I think constitutes a good Koi pond. To me, what the pond is made of is not that important. So long as it holds water, and can be trusted to do so in the long run, any type of construction will do just fine. All materials have their drawbacks, and advantages. You'll have to take into consideration that I am located in Florida, so my notions may not be valid where you are.

Concrete ponds have been around for many years. I don't see too many in my area, and I don't have one, myself, so I won't say too much about them. They have a definite advantage in strength, when properly built. Newer methods make them much less prone to hairline cracks and leaks. Could be wrong here, but I think they have less of a tendency to suffer from carbonate depletion than flexible liner ponds do. One downside I see would be the difficulty in making changes after the pond is built. But, the Law of Six P's comes into play here. Prior Planning Prevents Poor Performance, Possibly!

The flexible liner is the material most used in my neck of the woods. By "flexible liner," I'm talking about either EDPM (rubber) or HDPE, sold as Permalon. I do NOT consider swimming pool liners as suitable for ponds. They do have a place in temporary containment, especially on fish farms, or similar applications in the back yard. The key word here is "temporary."

More about flexible liner materials, on another page.

The shape of the pond should be devoid of sharp corners. By that, I mean to say the "corners" should be rounded, or built with a radius. Where the sides meet the bottom should also be rounded. The idea is to avoid any "dead spots," places where water is completely still. Water needs to circulate through out the pond. And that movement should push any sediment towards a bottom drain. To help with this circulation, you can direct part of the return from the filter to underwater "jets." These submerged water returns can be directed to sweep along the sides and/or bottom, to move sediment or suspended solids towards the bottom drain(s).

If the pond is not a square, rectangle, or round, and is more of a "free-form" design, it will likely have a greater opportunity for dead spots, or areas with little or no circulation. These will have to be addressed. The methods include the venturi, air lifts, air stone, and submerged water returns from the filter system.

On the subject of bottom drains, yes, I DO consider them a necessity in a Koi pond. In fact, most ponds would benefit from a bottom drain. In general, I'd not use anything smaller than a 4-inch bottom drain. There is some argument that in a smaller pond, a 3-inch bottom drain might be a better idea, because of the lower water velocity moving through it. As I see it, you don't want to under-size a bottom drain, because you could wind up with the part of the system that is being supplied by that bottom drain draw down too far when water is moved out of it.

If you use too large a bottom drain for the flow going through it, solids can settle out in the drain line. And this drain line, as you will see shortly, is not going to "waste," but ultimately feeding your filter.

For some thoughts on different types of bottom drains and a few alternatives to poking a hole in the bottom of your pond, there will be pages on those subjects.

This brings us to the filter section. You can do a lot wrong and get away with it in many areas. But NOT in the filter! If you go wrong here, you will spend a lot of time, money, and effort in making up for it. In fact, many of the "additives" and "treatments," are mostly due to so many people missing the mark on pond filtration. Come to think of it, that applies to the basic pond design, as well. This will become more apparent in the other pages that deal with design considerations.

Notice I did not mention biofiltration. Yes, biofiltration is of vital importance, but the term is often misused. There are actually two forms of filtration at work in a Koi pond. Biofiltration, where water with toxic chemistry (in the form of ammonia) is dealt with, and Mechanical filtration, where solid waste is the primary concern. These are two distinctly different processes!

You could save yourself a lot of reading here by referring to Peter Waddington's book, "Koi Kichi." Among other things, he includes in his book both discussion and drawings of an elegantly simple solution to a complex problem. Follow his lead; it will serve you well!

The design of the pond should be so that all heavy (sinking) solids pass down and out of the pond, through the bottom drain(s). The water, along with those solids, should wind up in the first section of the filter system, where the solids can be removed. This first section of the filter system can take several forms. My preference is the vortex chamber, or tank.

This will be continued in the Filter Systems section.

I think perhaps the most import consideration with Koi ponds, once the basic pond and filter system have been selected, is the stocking rate.

Unlike the biofilter, more is *not* better. 200 gallons per adult Koi, would be a maximum fish load, on a pond with a *really good* filter system and pond dynamics. One adult Koi per every 500 gallons would be better rate. In fact, this number would be a pretty good target, for most people. 1,000 gallons for each adult Koi would be very close to what I'd consider an ideal rate. Of course, you can go even farther, but I have to assume you'll be expecting to actually *see* your fish, once in a while!

Even if your Koi are smaller than their adult potential, stock them as if they were. Plan on your fish growing. Thinking that the pond and system is fine with the current number of Koi when they are less than adult size, means all this will change as they grow. If you aren't prepared to reduce the numbers as they grow, then you are setting yourself up for disaster.

If you keep the population to these numbers, your fish health problems will be minimized. It's hard to do sometimes, but if you want to do it right, you simply *must* keep the numbers in line! When you see that "just-gotta-have" Koi, you need to ask yourself, "Which Koi now in the pond, will I be willing to give away, or sell?" Still want that new one? Then you know what you have to do. And do it, quickly! Or, it will never get done and soon, you'll be stocking like a fish farm and experience all the pitfalls that go with it.

This is but the first in a series of articles. More will follow. Much more!

Mike S.

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