Acropora ID plus Yellow Goby

[Samw]

Got this nice frag during the summer. Can someone ID this coral for me?

Frag came from MH tank but is now under PC lights. Surprisingly, it seems to have become more purple under PC lights. Cool. 2nd photo shows the polyps retracted because of the dreaded Yellow Goby. Last photo is the recovery a few days after Goby was banished.