My 2 cents, If you are getting green water (microalgae) do a partail water change everyother day for a week or so, and while you are doing that make sure your tank doesn't get direct sunlight and that you turn off the light at night, If your tank is not planted yet add macro algae like elodea or cabomba, a few bunches of each, you don't even have to root them. They will outcompete the microalgae for nutrients. You should see a difference within a week or two.