Designed specifically for the Fluval FX4, FX5 and FX6 high performance canister filters, Bio-Foam+ pulls double duty as both an effective mechanical and biological media. Key Features : *Mechanical/Biological filter media *Large porous surface area supports expansive beneficial (nitrifying) bacteria growth *Effectively captures small particles and debris, particularly those that are not retained by the first stage of foam filtration *Custom fit for FX Series filters to increase filtration efficiency *Helps create a healthy aquarium and ideal water conditions *Rinse every 3 months *Replace every 6 months *Convenient 2-pack format *For use in freshwater and saltwater