Designed exclusively for Fluval Canister Filters, Fluval Bio-Foam provides exceptional biological and mechanical filtration. Its dense composition effectively traps any small particulate matter that is not captured by the first stage of foam filtration. It also features an intricate network of pores to provide optimal surface area for the growth of beneficial nitrifying bacteria. Fluval Bio-Foam helps keep your aquarium water clean, clear, and healthy! Designed for use in both freshwater and saltwater aquariums.