The CF300 is one of our most popular canister filters and you really can't beat it for the price. The 264 GPH multi-stage filtration system is ideal for fresh and saltwater aquariums ranging in size from 20 gallons to 75 gallons. The CF300 defies its low price because it comes equipped with all the necessary plumbing for installation and includes three large filtration media compartments allowing you to add the filtration media of your choice. The filtration media trays offer a fully customized filtration system to suit your specific aquatic needs. The CF300 includes three fine filter pads (white) and a single coarse filter sponge (blue) for enhanced Mechanical Filtration. With the addition of Aquatops Premium Activated Carbon, Ceramic Rings, or Bio-Balls (each sold separately), youll achieve superior filtration and crystal clear aquarium water. The CF300 canister filter has a convenient Prime Pump that eliminates the need for manual siphoning! Say good bye to a mouth full of aquarium water!!!. How Does the CF-300 Canister Filter Work?: Unfiltered aquarium water enters the CF Series Canister Filter and passes by the U.V. Sterilizing Bulb flowing down the stack of vertical cylinder cutouts to the bottom of the CF Filter. Then water is pushed up through the filtration media compartments; the bottom compartment first, the middle compartment second, and the top compartment third. The filtered aquarium water then returns from the CF Canister back into the aquarium. * U.V. Sterilizing Unit not available in CF300 but assembles and filters in the exact same manner as the CF-400 and CF-500*.