When I got green water I tried all the tricks, blacking out the tank, chemicals, water changes, bla bla bla. I finally broke down and bought a uv. Best investment ever! I would run it 2 days then turn it off for months until I got green water again. After going through that cycle maybe 3 times I'm happy to say that my tank is balanced enough that I've not used it in probably 6 months. Some people (no one on here) made me feel like a failure because I had green water and because I bought the uv, but I'm here to tell ya, you gotta do what's right for your tank and sometimes that means buying a uv. Good luck!!!