AquaClear BioMax Filter Insert contains BioMax ceramic rings. The surface of BioMax is made up of a complex pore system that allows bacteria to thrive. Each ceramic ring contains at least 100 square feet of surface area providing more biological power than a traditional cartridge. Use o the BioMax insert will provide optimal living space for beneficial bacteria and enhance the removal of ammonia and nitrites resulting in a healthy aquarium environment. Safe for fresh and saltwater use. Designed for use with AquaClear 20 (formerly AquaClear Mini) Power Filters.