These chemical sponge filter is designed to keep your aquarium clean . The filter provides mechanical and biological filtration for easy aquarium maintenance. As a mechanical filtration use the air-driven system to create a suction that allows the sponge to capture floating particles in the water and return filtered water to the tank. As a biological filtration, harmful wastes are biologically transformed into a relatively harmless substance by aerobic bacteria that accumulates in the sponge. This kind of sponge is also suitable for Discus breeding tanks, tropical fish tanks and fry stock tanks.