do you know if they are rathbunae shrimp versus wurrdmani? noth are types from the caribbean, both are great to have in a tank, however if you are lookign to control apitasia, the wuurdmani shrimp seem to do a better job at eating the pests, than the rathbunae, however oth will go after them. both specise are simultaneous hermaphrodites, so if you get a pair, one will turn into a male, the other a female. this usually takes about 19 days, and after that they will mate and spawn, which is great because it is a constatn source of food for your fish and corals!
good luck
jon