Aqua UV 57W 2 inch Classic UV Sterilizer The Classic Series UVs are ideal for ponds, aquariums, and water features. The Classics rugged design has features that allow for quick installation and easy maintenance. Aqua Ultraviolet UVs will clear your water in 3 to 5 days sometimes overnight and keep it that way. Performance is guaranteed when sized, installed and operated according to our instructions. Fresh Water Sterilizer: 1,500-3,000 gallons; Flowrate - 3,200 gph for 30,000 μw/cm2 Fresh Water Clarifier: up to 6,500 gallons; ideal for water gardens Salt Water Sterilizer: up to 355 gallons; Flowrate - 1,066gph for 90,000 μw/cm2 Dimensions: 26.25" X 4" X 2.5" Inlet: 2" slip, Outlet: 2" slip Available in white (Black special order only) Lightweight Unit Weighs: 5 lbs What is a Sterilizer? A sterilizer will eliminate green water and control bacteria. The Classic 57 Watt, will sterilize up to 3,000 gallons of fresh water or 355 gallons of salt water. What is a Clarifier? Used as a Clarifier the Classic 57 Watt, will control green water in a freshwater environment of up to 6,500 gallons that has 50% to 75% plant coverage and partial shade. What works best for Marine Tanks? In marine fish tanks (No reef or live rock) a flow rate matching those shown in the 75,000 or 90,000 column will be most effective at controlling fish disease. How do I size a UV for a Reef Tanks? In salt water reef environments choose a UV that matches your flow rate per hour in the 30,000 or 45,000 columns of our chart. Flow rates in the 75,000 and 90,000 columns will destroy the planktonic food supply for the reef.