I have one female betta and 2 cories, along with several fake plants. problem is, i noticed in the last few days that my cory's seemed to not be swimming around as much as they used to. finally found them tonight and pulled them from the tank as one was dead and the other was dying. Upon closer inspection of the cories, i found that the dead one had his (i dont know how to tell the gender on the cories sorry) caudal fin completely gone and the second cories was half gone. my only guess as to the reason for this is my female betta started fin-nipping them after a month of being in the same tank. No, there isnt anything sharp or that can catch the fins in my tank.
has anyone else experienced this problem? Recommendations? I was considering getting a few more to put back in there, but don't want to keep going through this every other month, if not more often.
tank specs: 10 gallon, filtered, heated, and all chemical levels within norms.
Plenty of fake plants and hiding places.
Fed every other day.