I have a betta in a 1g and yesterday I put a mirror behind his tank for 20 minutes but forgot about it and took a shower. When I got out and looked at him his bottom fin was spilt in half. It wasn't ragged and it didn't have any chew marks it was a clean spilt right down the middle of his bottom fin. Was the constant flaring and spreading his fins out what made it rip or what? Also should I put salt in the tank to help keep bacteria off the fin and help it recover faster?