The only truly natural ways to seal a pond will still allow some amount of leaking and seepage. This is because even the best natural clay sealants have tiny gaps between their particles that allow water to leak out. Putting in a layer of bentonite clay or smoothing the surface of raw clay soil can help a pond hold water, but it doesn’t compete with a real liner. While a flexible RPE liner is obviously not a natural material, it can play a role in an otherwise completely natural pond that you want to stay full year round.
RPE liners don’t leach out chemicals or kill off bacteria. Your lined pond will look just as natural and attract wildlife the same way as any naturally lined pond filled with clay. If you’re looking for a way to let frogs and other aquatic animals burrow into the bottom of the pond to hide over the winter, simply add sand or mud to the base over the liner. There’s no need to deal with a constantly leaking pond just to attract wildlife and enrich the environment. Make your natural pond with a manmade liner and you’ll be glad you did for the rest of its lifespan.
