Fluval Bio Foam Pads are specially designed for Fluval FX5/6 High Performance Canister Filters. Bio Foam Pads provide outstanding mechanical and biological filtration thanks to an intricate pore structure that offers a large surface area for the growth of helpful nitrifying bacteria. In addition, they trap small particles that are not retained by the first stage of foam filtration. Fluval Bio Foam Pads enhance biological filtration and effectively capture small particles and debris. For freshwater and marine environments.