Juwel Poly pad is used to catch coarse particles of dirt in the water. As a mechanical pre-filter, it protects the filter from rapid soiling so that you don't have to clean the other filter media more often. Suitable for use in both saltwater and freshwater aquariums. Suitable for Bioflow Compact and Bioflow Compact Super Filters installed in Rekord 600 & 800 aquariums.