As far as I'm aware, we had Carribean peppermint shrimps ... here's a photo of one of the 3 culprits.
http://www.canreef.com/photopost/sho...php?photo=2647
Good luck
... careful watching and an action plan for transfer into another tank in the event of deviant behaviour would be prudent (although your frustration level will sky rocket trying to catch them if they're in a tank with live rock)
