I have an algae problem. I water my greenhouse by pumping well water into an elevated tank then use the water after it warms to greenhouse temperature. Trouble is, I get an algal bloom inside the tank. The algae then covers the soil surface of the plants and all this has been a constant battle with fungicides for the plants, draining & cleaning the tank, and etc. Does anyone have a suggestion as to how to control the algae in the tank?