Tuesday night I bought a used 30 gallon tank that came everything, including the fish. After setting everything up, and getting the fish adjusted to the temperature, everything was going well. All the fish were doing great. The next day, around noon, my dalmation molly started laying on the gravel and breathing heavy, since then she will be down there for about 15 minutes breathing heavily, then come up for air for around 15 minutes. Once in a while she will swim around like normal but not often. She is still eating, I noticed today she ate most of the fish flakes herself, so I'm not if she is over eating. The temperature is at a normal 75, and the filter is working great. Does anyone know what the problem is? I know that she was attached the the previous owner, so I'm not sure if she is just stressed or what happened. The rest of the fish are doing fine. Thanks!