Look at the ends of the dorsal and anal fins. Males will have a pointed end, which extends out past the caudal peduncle; females will have shorter, rounder fins,
http/s1336.photobucket.com/albums/o641/wigancol/?action=view¤t=image_zps2be589fc.jpg this is a link to a pic of one of them but as I say still baby's and colour only just starting to come through hope I don't have 2 females lol