Interpet Cartridges for Corner Power Filter CPF3The black sponge will need to be replaced once every 3 months. The carbon filter cartridge clears and purifies water and the black sponge removes large waste. 3 x Filter Cartridges with carbon~ 1 x Black Sponge Keep your filters working hard with this multi pack of easy to replace filter cartridge for the Corner Power Filter CPF3 Replace monthly to keep your CPF Filter working like new, the carbon filter cartridge clears and purifies water and the