Our Beta fish is kept in a goldfish bowl. It is our 2nd Beta fish and we have used the same stones in the bowl as the last one. About 2 or 3 days after we clean out the bowl and add filtered water, there are lots of bubbles in areas floating at the top of the water and then a film starts to appear over the top of the water. When you stick your finger in the water and skim the top, there is a white milky residue on your finger. The fish becomes less active when this happens and holds it fins close to its body. We cleaned out the bowl and water about 3 days ago and had to do again today. The fish was very happy afterwards. What can it be? Or what could be causing it? We have used the same stones with the last 2 fish we had, first a beta and then a goldfish and never had a problem. We even tried switching out the stones. Is it the fish doing it? Help! Lisa