KollerCraft TOM Rapids Power Filter, 80 GPH Hang-on-the-tank filter ideal for nano, mini-reef, and other small aquariums (up to 20 gallons) Purifies aquarium's water while extracting unwanted fish waste and other debris Flow rate of 80 gallons per hour (GPH) Bio-Grid insert provides superb biological filtration Can be used for both freshwater and saltwater applications