Ultraviolet Clarifiers will give you the best possible water clarity. The distinctive spiral water guide design maximizes exposure to the beneficial UV rays. As algae passes through the unit, the UV light bleaches chlorophyll from the plant. The chlorophyll sticks together and lodges in the biological filter to decompose, turning into nutrients consumed by beneficial bacteria that render the nutrients harmless to pond life. Large ponds. 36 Watt, up to 4,000gal, flow rate approx 2,000GPH.