The Penn-Plax Cascade 300 Aquarium Filter works hard to keep the tank clean for your fish. With a flow rate of 300 GPH, this aquarium filter is great for tanks with a capacity of up to 100 gal. The Cascade 300 aquarium filter utilizes a quad-filtration system that has a polyfiber floss cartridge, activated carbon cartridge internal sponge and external bio-falls.