AquaClear 20 Foam Filter Inserts are replacement filter media for the AquaClear 20 Power Filter. The AquaClear 20 Foam Filter Insert is a mechanical filter media that effectively removes particles and debris from aquarium water. It also prevents particulate waste from prematurely clogging other media in the filter. Primarily a mechanical filtration media, it also provides powerful biological filtration as friendly bacteria eventually grow inside its pore structure. Exclusively designed for the AquaClear 20 Power Filter, the Foam Inserts are safe for fresh and saltwater aquariums. AquaClear creates a wide variety of products for freshwater tanks such as fish tank accessories, fish tank decorations, and aquarium filter media that is perfect for large and small fish tanks.