Aqua Ultraviolet A00266 Advantage 2000 8 Watt Sterilizer / Clarifier

This is an excellent unit in keeping my pond clear of algae! My little (100 gallons) outdoor pond was over grown with algae. I have to clean it at least once a week to keep the algae under control. The constant cleaning had stressed out my little koi (3" long) and none of them survived beyond 6 weeks. After adding this unit to my pond, the algae problem disappeared! My pond is clear and I can see the bottom of the pond! Also, my water lilies and my new gold fishes are alive and well.One small recommendation, keep the unit on at all time (like the instruction said)! After running it for three consecutive weeks, I turned it off and tried to see if the algae problem returned. With the unit off, the algae came back with a vengence. In less than 4 days, my water lilies and the pond wall are full of algae again!