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Koi Ponds

© Kirk Johnson

I have had koi in my garden's ponds for over fifteen years. They aren't really pets in the same way that my cats are pets; they are almost wild, but that is part of the reason why I enjoy them.

My original koi pond was narrow and shallow; it was only about 18 inches deep. I had considered using a fiberglass liner, but they weren't available in the shape that I wanted, so I lined the pond with polyethylene sheeting. The koi did fine for a couple of years until a family of raccoons discovered them. By this time, a 25 by 50 foot clay bottomed pond had been dug for fire protection; the koi which survived the raccoons were put in this pond. A few of my original koi are still alive; I have never measured them, but they must be over two feet long. The clay bottomed pond is now my lilypond. The koi don't damage the waterlilies, but they constantly churn up the mud, so I only see them when I feed them. The muddy water does protect the koi from the blue heron that often visits.

I have read that koi only reproduce when there has been a marked change in temperatures; this seems to be true, my koi have only reproduced twice, both times after unusually cold winters. Last winter was the coldest in the twenty years that I have lived here. It looked like the koi were mating this spring, but I haven't seen any babies yet.

I re-did my original koi pond in the autumn of 1997. It is now an irregular semi-circle 10 by 18 feet and three feet deep. The polyethylene liner had leaked, so this time I used a butyl rubber liner. It is supposed to last for at least 50 years and if it is damaged it is as easy to repair as a bicycle tire.

If your pond is surrounded by open ground, so that you can stretch out the butyl rubber liner in all four directions, it will stretch as you slowly fill the pond with water and have few wrinkles. My liner has wrinkles because I wanted to keep the existing plantings, this is something to think about when deciding where to locate a pond. The south side of this pond is bordered by a narrow deck and is fastened to the deck with a cap of pressure treated wood; the other sides of the pond are edged with large rocks. The rocks sit on a shelf which is below water level and they are mortared together. The shelf is excavated so that the stones tip away from the pond.

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