http://tinyurl.com/nlyrp43Pondmaster 02920 20-Watt Ultra-Violet-Light Pond Water ClarifierProduct Review Click on the link for more reviews20-watt UV water clarifier effectively kills suspended algae, eliminating green-water pond problemsSuitable for medium ponds up to 3000 gallons using pumps up to 1800 gphVortex flow design and slim diameter provides added efficiency; installable in or outside pondIncludes 9000-hour 20-watt lamp, transformer, 18-foot power cord, and watertight quartz sleeveMeasures approximately 19 by 4 inches; 1-year warranty