UltraClear Koi Clay 4 Pound Container UltraClear Koi Clay helps to maintain a clear, high quality water environment for your Koi or gold fish in your pond Trace elements for improved bone and scale growth, blood clotting and reduced loss of sodium and potassium from fish blood. It contains essential silica for removing harmful toxins and heavy metals UltraClear Koi Clay is 100% Bentonite Clay Bentonite Clay and the size or the particles is critical for bonding with and absorbing toxins such as heavy metals and pesticides that may enter the pond habitat.