Aqua UV 25W 2 inch Classic UV Sterilizer The Classic Series UV's are ideal for ponds, aquariums, and water features. The Classic's rugged design has features that allow for quick installation and easy maintenance. Aqua Ultraviolet UV's 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: 500-1,200 gallons; Flowrate - 1,200 gph for 30,000 µw/cm2 Fresh Water Clarifier: up to 4,000 gallons; ideal for water gardens Salt Water Sterilizer: up to 150 gallons; Flowrate - 400gph for 90,000 µw/cm2 Dimensions: 26.25" X 4" X 2.5" Inlet: 2" slip, Outlet: 2" slip Available in white only. Lightweight Unit Weighs: 5 lbs What is a Sterilizer? A sterilizer will eliminate green water and control bacteria. The Classic 25 Watt, will sterilize up to 1,200 gallons of fresh water or 150 gallons of salt water. What is a Clarifier? Used as a Clarifier the Classic 25 Watt, will control green water in a freshwater environment of up to 4,000 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.