AquaClear 70 Foam Filter Insert is a mechanical filter media that effectively removes particles and debris from aquarium water. It also prevents particulate waste from permaturely clogging other media in the filter. Primarily a mechanical filtration media, it also provides powerful biological filtration as friendly bacteria eventuyally grow inside its porous structure. Exclusively designed for the AquaClear 70 Power flter but the foam filter is safe for fresh and saltwater aquariums. 3 per package.