The carbon filter cartridge clears and purifies water and the black sponge removes large waste. Filter cartridge floss will become blocked with trapped material and the carbon capacity for removing toxins will become exhausted. Replace the cartridge every month to keep your aquarium healthy, clean and clear. The black sponge will need to be replaced once every 3 months. The box contains Technical specifications. Keep your filters working hard with this multi pack of easy to replace filter cartridge for the Corner Power Filter CPF2 (pack contains 3 x cartridge filter with carbon, 1 x black sponge) FOR CRYSTAL CLEAR WATER - the carbon filter cartridge clears and purifies water and the black sponge removes large waste EASY FIT - simply remove the old filter cartridge and sponge and pop in the new ones KEEP YOUR FILTER RUNNING LIKE NEW - the filter cartridge floss will become blocked with trapped material and the carbon capacity for removing toxins will become exhausted (replace monthly), the black sponge should be replaced once every 3 months LIFE SUPPORT - for coldwater or tropical aquariums. The Service Pack for Corner Power aquarium filter by Interpet is a convenient and easy-to-use solution for maintaining your aquarium's filtration system.