If this is a 10g, then I would upgrade as I personally wouldn't put corys (even if they are pygmy or c. habrosus) in anything less than a 20g, but ideally in a 20 long.It’s actually been the opposite, but there hasn’t been any significant damage, my betta is part crown tail I think, he has had the deformities in the fins for forever now, and the betta has been aggressive to the swordtail a bit. I have 6 pepper cories and 15 shrimp and some bladder snails but nothing else. I just have to find someone to take the swordtail