Penn Plax Cascade 400 Submersible Aquarium Filter Cleans Up to 20 Gallon Fish Tank With Physical, Chemical, and Biological Filtration Fully submersible aquarium filter quietly delivers 110 gallons per hour of crystal clear water for your fresh or marine aquarium from 10 to 20 gallons in size. Activated carbon cartridge removes harmful chemicals, toxins, odors, discoloration, and other contaminants for your aquarium. Internal sponge optimizes colonization of beneficial aerobic bacteria. Large capacity aquarium filter cup allows you to choose your own filter medium. Pump head with adjustable and directional water flow. Cascade internal filters provide better filtration; physical, chemical and biological while also aerating water. Spray bar option allows you to distribute water evenly helping aerate your tank. Fish tank filter can be placed horizontally and is easily hidden.