The SunSun HW-304B external 5-stage canister filter with built in UV sterilizer is ideal for tanks up to 150 gallon freshwater or saltwater aquarium. It is capable of handling up to 525 gallons per hour with 4 flexible media trays that allow you to add your media such as SunSun's activated carbons, ceramic rings or bio-balls (included) to achieve excellent mechanical, chemical and biological filtration. The HW-304B has a built in 9 Watt UV sterilizer to help kill algae spores and bacteria, promoting clear crystal water. The HW-304B canister filter also has a convenient self-priming pump that eliminates the need for manual siphoning.