AquaClear Foam Filter Insert provides mechanical filtration by trapping particles and debris in addition to providing biological filtration. Exclusively designed for the AquaClear Power Filter, the insert is safe for fresh and saltwater aquariums. Available in the following sizes: Filter Insert for AquaClear 20 single or 3 pack Filter Insert for AquaClear 30 single or 3 pack Filter Insert for AquaClear 50 single or 3 pack Filter Insert for AquaClear 70 single or 3 pack Filter Insert for AquaClear 110 single