Hydrodynamic Mattenfilter HMF Sponge Filter for Perfecto or Marineland Aquarium Tropical Fish Tank Filtration Sponge Filter for Tropical Fish Tank Aquariums 40 PPI Reticulated Foam won't collapse or clog Provides greatest amount of surface area for beneficial bacteria to colonize 100% freshwater and saltwater fish safe Hydrodynamic Sponge Filter Technology Made in the USA