i asked the very same question a while ago and no one ever replied......but if i were take a guess you probably cant maybye they are like clownfish and the more dominate one becomes the male
Well, not really an answer, but I have three in my tank, and two have paired up on one side and one on the other side (100 gallons). BUT they all look exactly the same to me
I've done lots of searches on this and you can't tell. they will pair up or kill each other when mature. I've seen many pictures of pairs and they look ezactly alike.