I've got cloudy water and my water tests are fine. My thoughts are that I've got some algae going, but the tank isn't in sunlight. It sits in front of a window, but the window faces north. The cloudiness isn't green either...it's just, well, cloudy. I just finished medicating the tank, but the medication package explicitly noted that the tablets don't cause water coloration. I did a 50% change right after I finished the 5-day medication, but still I've noticed cloudiness for a little while before I started with the tablets.