This BioCube UV upgrade kills free-floating green water algae, parasites and harmful bacteria. The sterilizer attaches directly to the built-in BioCube pump for easy setup and use (if used with a different pump the flow rate should not exceed 300 gph). Compatible with all Coralife and Oceanic BioCubes Low-Voltage ballast and 5 watt bulb ideal for small aquariums This UV should only be used submersed. Do not use as an external UV sterilizer. Tubing Size Connections: 1/2 or 12mm I.D. tubing