Polyfiber floss cartridge traps floating particle matter Carbon cartridge removes harmful chemicals Internal sponge optimizes beneficial aerobic bacteria External bio-falls assist in ammonia and nitrate removal Offered in several sizes for several tank sizes. Hanging aquarium filter has poyfiber floss cartridge traps. Clean and remove harmful chemicals in your fish aquarium. Internal sponge optimizes beneficial aerobic bacteria for a healthy environment for your fish. External bio-falls assist in ammonia and nitrate removal harmful to tank pets. Available in size options. About Penn Plax: Penn-Plax is a family-owned company in operation since 1959. They specialize in creating excellent pet supplies for animals both great and small. Best known for producing pet products at affordable prices, the Penn-Plax brand is synonymous with innovation and quality, keeping your pet foremost in mind.