The SunSun HW-304B 5-Stage External Canister Filter with a built-in UV sterilizer is ideal for tanks up to 500 liters. 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 (each sold separately) 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. The UV sterilizer also promotes clear crystal water. The HW-304B canister filter also has a convenient self-priming pump that eliminates the need for manual siphoning.