I just found this info not too long ago.
Green Acropora commensal shrimp
Scientific name : Coralliocaris graminea
Tiny commensal shrimp very difficult to see, it lives amongst the branches of Acropora hard corals. Distinctive colour pattern, with white, green and brown longitudinal lines. 1 cm.
Other commensal shrimps share the same environment, but the colour pattern of this one is unique and distinctive.
Associated organisms
Always associated with Acropora hard corals, hidden amongst the branches, deeper during the day while at night it is possible to spot it closer to the coral surface.
Habitat: Back reef, Reef front
Distribution: Indo-West Pacific
http://www.flickr.com/photos/artour_a/243275702/
Cool looking thing. I let him back into the tank.