Our Premium Cut-to-Fit Aquarium Filter Foam provides essential two-in-one filtration: mechanical debris trapping and biological surface area for nitrifying bacteria. Made from durable, non-toxic open-cell polyurethane (Polyether), these sheets are easily cut with scissors to fit any filter type (Canister, Sump, Internal, or DIY Hamburg Mattenfilters). Available in graded densities (PPI): Choose Coarse ($10/20\text{ PPI}$) for initial large debris removal, Medium ($30\text{ PPI}$) for balanced use, and Fine ($40/50\text{ PPI}$) for crystal-clear water polishing. Layering these grades ensures maximum efficiency and longer intervals between cleanings.