Zoo Med's Biological Ceramic Media is an integral part of the NANO filtration system. The ceramic media aids in turning harmful toxic nitrogenous waste (produced by your fish), into harmless nitrates. Biological ceramic media is one step to removing harmful toxins in your nano tank. We also recommend weekly water changes of at least 20%. When adding tap water (after a water change) make sure you add Zoo Med's Reptisafe to remove chlorine and chloramines.