Bio Foam Filter Media is a high porosity open-cell polyurethane foam filter sponge designed to provide both mechanical and biological water filtration in fish ponds, aquariums and aquaculture filtration systems. With its unique open-cell structure creating a massive surface area for beneficial bacteria colonization, Bio Foam serves as the living heart of any biological filtration system, breaking down harmful ammonia and nitrite into safer compounds to maintain healthy water chemistry for your fish.