I have a 60g tank that has a black moor goldfish, a oranda goldfish, a normal fantail and a cold water catfish that never comes out. I started off with the black moor and then decided to get another goldfish (the fantail). The lady at my LFS asked me what fish I wanted and cause they were all the same I just said any (big mistake). She then found a very small fantail at the back and I thought that it was just a baby so I got it. It's been 5 months he hasn't grown. He is always floating up the top near the corner of the tank and seems scared and looks like he's gasping for air. He eats but then goes back and when he swims he shakes his whole body. He's fins are shredded cause of the other two I think. The other two are just goo and getting very big. Soo what's wrong with the fantail??