Hi,
I found this little baby crab 2 months ago on a frag.  I originally put it in my nano and after 2 months I am now closing down my nano.  I did not see the crab for a month or more so I thought it was dead but it is alive and grew like 3 time the original size.  It is now nearly 3" from one side to the other with the legs.  The body is about the size of a quarter.
I think it's an emerald crab of some sort.  It never dammaged any of my coral, or attacked anything either.  Seem to be reef safe so far.
http://www.youtube.com/watch?v=RtmMN...yer_detailpage