BioKer is comprised of a very fine grained ceramic material which offers a large surface area to develop the beneficial bacteria responsible for biological filtration (Nitrosomas and Nitrobacter). BioKerâs micropores offer a self-cleaning effect, while making the external surface appear smooth. The beneficial bacteria that BioKer develops help to keep aquarium water clean and crystal clear, increasing the health of the inhabitants. Ideal for all internal and external filters. Instructions: Rinse the product under running water to eliminate superfine particles before placing it into the filter basket. BioKer does not wear out and does not lose its effectiveness over time.