TetraPond GreenFree UV Clarifiers provide permanent control of suspended algae which cause green water. Heavy algae blooms are removed in most ponds within 5 days, keeping the pond algae free. This means water clarity is improved while reducing pond maintenance. Each unit is compact, durable, easy-to-install and energy efficient. The most efficient flow rate is 50% of total pond volume. The UV Clarifier is not submersible and should be brought in during the winter months when temperatures are at or below freezing.