i love mine!!! his name is Piere and he'll wave at me and everything. you could put 1 male and 1 female in a 10 gallon. if you look under he crab (i usually use a clear bag or a betta cup and turn it upside down) the females vent will look like half of an O and the male will look like and upside down V.
Do you know the scientific name of the ones you have? And do they mate easily? How big do they get? I will need to hide them from my siblings, I think they would cook them!!!