I just picked up 2 Ghost Shrimp as a test and nanny's to see how they will fair in the tank. One I know is female cuz she's huge and pregnant. The other is much smaller and looks like a small non-pregnant version of the big one. The people at the pet store don't know how to tell the genders apart. I tried from what people said in another thread and I have 0 clue. I will try to provide a picture soon, but as of right now they are acclimating to the tank.