I have been building ponds, water features, maintain fish ponds for 24 years. I get asked a lot about uv lights for ponds, instead of using algicide. A lot of homeowners are worried/scared of using algicide in there ponds, worried might use to much and kill their fish. When I am done with a new pond or cleaning out a pond. I go over everything with you on how much to use in your pond, when the best time of the day to treat your pond. I will mark on the the container and on a measuring cup of how much to use.