Keep your tank clean and clear with the genuine Penn Plax filter cartridge to fit your Cascade 150 GPH Model CPF3 or 200 GPH Model CPF4 hang-on power filters. The bio sponge filter removes dirt and debri from your aquarium tank keeping your aquarium clean and clear. Filter sponge optimizes the colonization of beneficial aerobic bacteria which prevents the water from becoming cloudy and harming fish. Perfectly cut to fit into the Cascade 150 or 200 Hang On Filter tray without any gaps which could allow pollutants to re-enter the water.