Fluval Edge Foam Biomax Kit includes 1x foam block and 1x bag of Biomax. The Fluval Edge Foam Biomax Kit contains a foam pad that removes medium to large particles and is the mechanical filtration stage. It exploits valuable bacteria in the aquarium and maintains a balanced environment. Fluval Edge Foam Biomax Kit also comes with one bag of BioMax, which needs to be renewed every 2 to 3 months the Biomax is the main source of bacteria that flourish on the surface of the the porous surface of the media. This is the biological stage of the filter.