Cermedia, the makers of MarinePure Biofilter Media have created an ultra high surface ceramic biofilter media that will reduce nitrites, ammonia and nitrates from your fish aquarium or koi pond system for years to come without the need for replacement. MarinePure's Thin Bio-Film Technology promotes better bacteria growth that can be used in trickle filters, canister filters, media reactors or in areas where water can be passed through the media such as a sump compartment. 1½" Spheres (3.8 cm in diametre) 2Litres, Designed for Ammonia and Nitrite Removal in fish tanks.