Xinyou XY-180 Super Biochemical Sponge Filter This super biochemical sponge filter is a filter that keeps your aquarium always clean . The filter provides mechanical and biological filtration for easy aquarium maintenance. As a mechanical filtration , it use the air – driven system to create suction , that allows the sponge to capture floating particles in the water and returned filtered water to tank . As a biological filtration , harmful wastes are biologically transformed into a relatively harmless substance by aerobic bacteria that accumulated in the sponge . This kind of sponge is also suitable for Discus breeding tanks , small tropical fish tanks .