The Ultra-Violet Stainless Steel Water Clarifier kills suspended algae with UV light. This easy to use clarifier ensures 100% clarity. As water passes through the rays of the UV lamp, located inside each unit, it makes algae clump together so it can be removed by the pond's filter, eliminating green water. This stainless steel water clarifier has up to 35% more UV efficiency due to the reflective stainless steel interior.