Penn-Plax Cascade revolutionary bio-falls quad filtration system. Mechanical polyfiber floss cartridge traps floating particulate matter. A chemically activated carbon cartridge removes harmful chemicals, toxins, odors, discoloration, and other contaminants. Biological internal sponge optimizes colonization of beneficial aerobic bacteria. Removes ammonia and nitrites keeping the aquarium healthy. External bio-falls wet/dry biological booster for additional ammonia and nitrites removal. Enhances oxygen exchange for maximum water oxygenation.From the manufacturer:Penn-Plax is a family-owned business that was established in 1956 in Brooklyn, New York. Over the years our goal remains the same: to enhance the pet ownership experience.We specialize in creating excellent pet supplies for animals, both great and small. We're best known for producing pet products at affordable prices. Our brand, Penn-Plax, is synonymous with innovation and quality, keeping your pet foremost in mind.