The CF-400UV has become a very popular canister filter for the price and performance. The 370GPH, 3+1 filtration system is ideal for fresh and saltwater aquariums ranging in size from 75 gallons to 125 gallons. The integrated 9 watt UV sterilizer helps keep your aquarium healthy and crystal clear. The CF400-UV defies its low price because it comes equipped not only with a UV sterilizer but 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 customizable filtration system to suit your specific aquatic needs. The CF400-UV includes three fine filter pads (white) and a single coarse filter sponge (blue) for enhanced mechanical filtration. With the included AquaTop Premium Activated Carbon, Ceramic Rings, and Bio-Balls you'll achieve superior filtration and crystal clear aquarium water. The CF400-UV 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-400UV Canister Filter Work?: Unfiltered aquarium water enters the CF Series Canister Filter and passes by the UV 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 compartment; 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. The CF-400UV canister filter also includes a built-in 9 Watt UV sterilizer to help kill algae spores and bacteria, promoting crystal clear water. Premium Activated Carbon: (2) PSAC-350 will cover one CF-400 media tray, (2) PSAC-720 will cover a CF-500 media tray. Ceramic Rings: (2) PQR-400 will cover one CF-400 media tray, (2) PQR-800 will cover a CF-500 media tray. Bio-Balls: MBB-26 (1-2) should be used on a media tray depending on application.