Cut it off as close to the rock as possible then put a lot of flow on the area it was growing. Chances are you won't get rid of it completely without having to replace or scrape the rocks off.
I had lots. use a razor and go rate at the base of the rock. if you slowly lift the "foot" of the coral it doesnt rip and eventually u can get a finger under it, much stronger tissure and it comes rate off doesnt even leave any on the rock! Was super easy and saved all the slime/juice from cuttin them off.