I kept one for quite some time in 02'. I got it the size of a quarter, it grew to be maybe 5 inches or so across in less then a year, I turned it back to the LFS.
This is the first I have ever heard of a small species of the animal. You sure on that?
IME they can flip over a 15 lbs rock, so make sure your stuff is heavy and all of your corals attached or glued down well.
They are very very fun to watch. When they get acclimated to the tank they will be out and about more often.
I have had one disappear for a few weeks at a time. I took out the molt thinking the crab was dead (I was a newb and never heard of a molt before, kinda made an idiot about myself over the whole thing), I was quite surprised to see it pop up later.
They are fun animals, but do to there growth, adult size, and talent of knocking things over, I doubt I'll ever try again.
JME