as early as 3" you can tell the sex. The females first third of their dorsal fin are black and they have a more black bottom half of the body than the males. Mine are 6", had them for a year. more aggressive than any fish I have now. (red terrors, black nasties, umbriferum, carpinitis) When they bite, they take chunks out rather than initially just warning their enemies like most fish do. I wouldnt keep them with anything after they hit the 4" mark. Especially each other unless they are a pair.
these are from Rapps.
these are from Rapps.
