Tetra GreenFree Ultraviolet Pond ClarifierHelp keep your pond clear with Tetras GreenFree Ultraviolet Pond Clarifier. This device uses ultraviolet light to destroy suspended green algae by targeting the reproductive ability of single celled algae. Once the algae are destroyed, they are pumped out of the clarifier, clumped and removed by your ponds filtration system. Tetras GreenFree Ultraviolet Pond Clarifier installs in minutes, is easy to use and conceal, and can help remove algae blooms in