I don't see rot on any fins, only biting. And i read someone wrote that it is possible that betta can bite even dorsal fins. I have no idea how but yes someone who is on the forum long time wrote that it is possible.
You set up new tank, did you move it to new place or it at the same place the old one was? The reason i ask may be try to move it ,may be it will help, more toys you can even try to put outside of the tank?
Btw he not looking bloated any more . Just be careful with those freeze dried bw as they can be cause of the bloating. You can feed with it abot 2-3 times a week as a snack.
Last edited by ANHEL123; 07-19-2013 at 10:16 PM.