The most effective way of preventing green water and maintaining optimal conditions in a pond is by incorporating UV sterilization as a part of your pond filtration. The addition of a UV sterilizer/clarifier not only helps control green water, and the suspended algae in your pond, but is an efficient way to control algae while ensuring optimal pond conditions for fish and plants. The Grech CUV-136 36 watt UV Light Pond Water Clarifier for use with pumps up to 1188gph, in ponds up to 9250 gallons. High-performance UV bulb ensures professional power while ease of installation and maintenance make it the right unit for new or existing ponds or water gardens. Included 3/4″, 1″, 1-1/4″ and 1-1/2″ fittings. For peak performance, UV bulb should be replaced after 8,000 hours (about once every 11 months of operation).