My 65g tall tank has had slight green water. I did not paint the back of the tank and it has a white wall behind it. I cover 3/4 of the tank with a car sun screen because the sun shines on the tank for about an an hour. The room is very bright (well not today its raining). The filter gets a lot of green black algae too. I change half the water once a week. This tank is sitting in the same place as my old 45g. It has been running great phrams. I use a 18w inline filter. I just replaced the bulb in May. I hate what I did yesterday. I tried to use an increase of the excel. Well 7 hours later I lost my breeding pair of Discus and my Sids. Other fish are fine. Any idea's on how to get rid of this green water. Had my old tank for 4years and I am doing the exact same as I did before. EI ferts and excel.