Niger Trigger Pairing

[fivesmallworlds]

Anyone out there know how to tell a male from female niger trigger? I'm interested in putting together a pair, not sure if I'll bother trying to breed them, just would like to see them paired.

If I get 2 juvs. will they fight for dominance then pair up? or is it possible to pair up 2 med. or large triggers?

Thanks in Advance!