URGENT! HELP! Corydora habrosus

[jaela]

Hey guys,

I moved my betta girl in with the cories yesterday because they all looked fine, and now one of them is displaying the same symptoms as the one I lost. D: The thing is, it looks like one of his fins is torn up, so I don't know if he's doing badly for the same reason as the other guy, or if my betta girl got to him. I monitored her when I put her in and at the time she seemed to mostly ignore the cories, but she's pretty aggressive so I wouldn't be surprised at all if she got to him.
What do I do? Do I need to move my girl back out into her 2gal in case it was her, so she doesn't hurt anyone else? I don't want to keep going through this heartache with my cories, but I also don't want to stress out Ann by moving her again if she didn't do anything... =\