The CF500-UV takes UV canister filters to the highest level. This 525 GPH 4+1 filtration system is ideal for fresh and saltwater aquariums up to 175 gallons. The integrated 9 watt UV Sterilizer helps keep your aquarium healthy and crystal clear. The CF500-UV defies its low price because it comes equipped not only with a UV Sterilizer but all the necessary plumbing for installation and includes four 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 CF500-UV includes four 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), you'll achieve superior filtration and crystal clear aquarium water. The CF500-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-500 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. The CF-500UV has 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.