Dependable clarifiers use ultraviolet light to destroy the reproductive ability of suspended algae. Dead algae clump together in particles large enough to be removed by filtration, leaving the pond clearer. GreenFree® clarifiers usually remove heavy algae blooms within five days and keep the pond algae-free. They are easy to conceal, durable, and install in minutes. UL listed. 3-year limited warranty. 15 foot power cord.