SunSun HW-303B 4-Stage External Canister Aquarium Filter w/ UV sterilizer 365GPH Canister filters for aquariums use high water pressure, from a properly powered pump, to force water through the dense filter media. A pump can draw water from an under-gravel filter, and run it into a canister for double filtration 3 media trays capable of handling your choice of filtration media; Comes with an adjustable spray bar. This is a helpful feature if you want to adjust the output flow from the filter Built in 9 Watt UV sterilizer to help kill algae spores and bacteria, promoting crystal clear water Convenient self-priming pump that eliminates the need for manual siphoning; Single valve disconnect & priming pump ease routine maintenance Provides quiet, efficient filtration for fresh and saltwater aquariums is great for living rooms, offices or bedrooms