I know Jacks very well.......and I would guess more to "it" being female....but I'm sorry don't buy another especially if you are trying to pair them up untill "it" is a little bigger......USUALLY the females will have a lot of blue blotches on their gill plates and on about one third of their body they will have blue patches.......The males usually only have a few blue small patches on their faces and blue patches covering them all the way down their bodies.......I HAVE SOME PICS OF MY JACKS (BREEDING PAIR) IN MY PHOTO AREA.......check them out Nicksplosion