Pondmaster Submersible UV Clarifier (20 Watt) – A submersible ultraviolet clarifier designed to eliminate green water and algae in ponds up to roughly 3,000 gallons. This 20W UV unit can be used submerged or inline and features a vortex flow design to maximize water exposure to the UV light. It includes a long-life UV lamp in a watertight quartz sleeve and glowing indicator rings to show it’s operating. By sterilizing algae and bacteria, it keeps pond water clear and healthy.