theyre very easy, you just have to wait until theyre a lil bigger maybe. Females have pinkish or orange on the sides of their bellies (speckled with orange or pink sometimes when theyre small). Males are usually bigger and have longer fins.
NO cons are rare because they breed so easily. Females have orange on their sides, males don't. Simple. They will breed every month though so be careful. 2 cons can turn into 500 in a few months.