I have some new live rock from KP Aquatics, and this came in on one of them. I expected it would die off in my curing and QT process, but it survived and seems to be thriving now. It seems to have polyps of some kind that I didn't notice when in QT, as they wave around in the flow in the tank. Hasn't really colored up much (maybe just slightly green, but otherwise essentially still brown) since added. Maybe some kind of short goniopora?