Help, I don’t know what is wrong with my Betta. I have had him for about three weeks. I got him from petco because I felt bad for him and thought I could help. His water was dirty and his fins were crimped. He did fine after a couple of days being placed in his tank, but only for about three days. He then went back to crimped fins. He is still eating but having difficulty swimming and he sits behind the filter mostly. I had his water tested recently and it was fine. It appears that he is swollen on one side back towards his tail.