Cloudy Water

[rdebonis]

I have a new tank that was set up 3 weeks ago and the water is still cloudy. There is no trace of ammonia. I do 30% water changes twice a week, but the water still gets mildly cloudy. I am not overfeeding the fish. I have 6 Albino Corydorus Paleatus juveniles (up to 1") in a 10 gallon tank with a Tetra Hang On power filter and a small box filter. There is an odor in the tank and I have vacuumed the gravel a number of times. Everything points to overfeeding, the odor and the debris in the tank when I do water changes or vacuuming, but I am only feeding the fish 1 Tetramin Bottom Feeder tablet or 2 Shrimp Pellets per day. I have never had this problem before. The tank is used as a quarantine tank, with gravel and artificial plants. The fish are very healthy and are feeding with no problem. What up with the cloudy water and the mild odor? How do I get rid of it, without breaking down the whole tank. Could the gravel have been contaminated or perhaps the artificial plants. I washed everything before I used it. Very Very STRANGE, This is a first for me?