While there is no product that directly eliminates leeches, there are a few tricks that may just help reduce their numbers in your pond or lake.
A large leech population can indicate a low fish population. Leeches are almost a given in every pond, and a healthy fish population helps with leech control. One thing to consider is introducing bass or bluegill to your pond. The appropriate stocking for a 1 acre pond is 600-1000 bluegill and 200 bass in the spring or fall months. The cooler temperatures and higher oxygen levels are factors that allow for an easier transition for the fish.
Leeches are often times found in and around the muck, especially in the more shallow areas of the pond. Muck is decayed vegetation that ends up being a source of rich nutrients for different wildlife and plant life. The main method in deterring leeches is to get a hold on your muck problem.
We have two muck products depending on how much you are dealing with. For 6+ inches of muck in more concentrated areas, we recommend Muck Doctor. For smaller amounts, we have Natural Pond Cleaner. Both are composed of beneficial bacteria that helps clear out the muck and reduce any bad smells. Muck Doctor is a concentrated spike form that is dropped in the desired treatment location. Natural Pond Cleaner is more of a muck maintenance product that can be poured in monthly.