It is really difficult if they are about the same size. Males are bigger and females smaller. If the female is full of eggs, her belly will look full and if she is well rounded, this is the best marker for females. IF neither is well rounded, feed them well for a couple weeks or so with live foods to get them in breeding condition. Then it should be easy. If neither plump up, then you probably have two males.
IF you look at the first two to four spines of the dorsal fin, males usually have much higher spines than females.
It is really difficult if they are about the same size. Males are bigger and females smaller. If the female is full of eggs, her belly will look full and if she is well rounded, this is the best marker for females. IF neither is well rounded, feed them well for a couple weeks or so with live foods to get them in breeding condition. Then it should be easy. If neither plump up, then you probably have two males.
IF you look at the first two to four spines of the dorsal fin, males usually have much higher spines than females.