I purchased to male bettas a couple months ago and at the pet store they told me to get a tank with a devider in it and they would be fine. Unfortunately they were not and one of the males started to attack the other through the devider and slightly damaged the fins of one of them. So I quickly separated them into separate 2.5 gallon tanks. The attacker fish is thriving and doing very well. The one that was attacked did very well for weeks after, but now he is always swimming/floating on his side at the surface and behaves very bizarely. Sometimes when I walk in the room he will VERY quickly shoot around the tank in like a little ball, hit the rocks, and come back up to the surface or swim strangely and flop all around. His fins are looking a little bit more raggedy as well. I clean the tank regularly and make sure it is at an appropriate temperature and the water is conditioned, so I don't understand why he in becoming so unhealthy.. What is wrong with him? Is there anything I can do?