by Mike Anger
Pond building is a project most of us will undertake at some point as we continue to raise Koi. Many of us first started with the introduction of a water feature, added plants, perhaps some goldfish and then Koi. A few of us bought a house where the prior owner had some type of pond or fountain, and we too evolved into having a Koi pond. Whatever way you arrived here, we all wrestled with similar questions: how large, how much to spend what kind of filters, and what do we make it out of.
The simplest ponds are made of preformed polyethylene. The corners are already rounded, the bottoms sloped, bottom drains are already in place and all that’s needed is its installation, a waterfall and water. Its disadvantages are its fixed shape and size, and the risk of pH crash as this material is inert (if the entire pond, return and waterfall are made of the same material). While it may seem to be a simple option, the preformed ponds are very hard to get level while also being well supported. Another problem are the plant shelves, which make perfect places for Herons and other predators to wade and kill your Koi.
Another easier pond to build is a liner pond. Here you have fairly low cost, as well as shape and size flexibility. It can suffer from leaks from plumbing fixtures through it, and tears or punctures. It may wrinkle and fold, interfering with water circulation and catching and trapping detritus, and it is difficult to hide the liner that extends above the water line. Lke polyethylene, may result in pH crash. Do not build plant shelves when designing a liner pond, again because it will encourage predators. Sides should be basically vertical, and ideally, all Koi ponds should be 2 feet deeper than the deepest frost depth in your area.
Fiberglass has the advantages of flexibility of size and shape, smooth corners with no folds or wrinkles. It has few problems with leaks, is very durable and can be remodeled. It can be quite expensive, may leach some chemicals that are harmful to Koi if the resin is not fully cured, and it too is at risk for pH crash.
Concrete ponds tend to be very popular. They are quite durable and can be in any size or shape. They do take a bit of planning (and expense). They require rebar for support and strength. Once installed, concrete must “cure.” This process strengthens the concrete reducing the chances of cracks and leaks. Compounds that leach out of concrete will raise the pH to lethal levels, uless the pond is cured. Curing requires adding water and muriatic acid. Some opt for a liner or spray-on lining over their concrete. Of course, the advantage of properly cured concrete is that the pond may never be prone to a pH crash, and will also have sufficient alklinity to insure healthy fish and filters.
Ponds produced out of cinderblock or bricks need a plaster coat or some other type of waterproofing material. Any type of masonry pond that needs a final plaster coat must have it done all at once. This is because in order for it to be waterproof, all edges of that plaster have to cure at the same time.
When planning on building a pond, whether your first or last, carefully weigh the pros and cons of each type of construction, utilize the expertise of K.O.I., and consider taking the Pond Construction course #202 BEFORE you build. Spending time to learn in advance will save time and money, and help you to get exactly the pond that you desire.