I have an established 32gal community tank with a mixture of mostly non aggressive fish, including one which was sold to me from Petland as a female swordtail (I questioned it but she assured me) but I'm fairly certain is a male molly. Lately he's been flaring a lot and biting my blackskirt tetra's fins. I imagine the issue is my gender ratio being off, but I wanted a positive species ID before trying to correct it. (He's the black one.) Thanks.