I have tested my tap water many times over the years and its always been good and there is no film on top of the water. The problem I think Myklien2 hit dead on. The tank is overcrowded and as much as I hate to admit overfeeding, caused the biological filter to break down the ammonia and nitrites to nitrates, which made the water cloudy and caused the fish to gasp for air. Two water changes a week, air stones and less food at feeding have helped, the water is not cloudy, and the fish seem back to normal. Now I have to find new homes for a few of my fish to help the overcrowding issue, even though I'm finding that very difficult to give any of my buddies up.