Aiptasia anemone. Pests that are near impossible to get rid of. Animals that will eat them are peppermint shrimp, bergia nudibranchs, file fish, Kleiny butterfly fish but none of them are guaranteed to even touch them. There are products out there to kill them and they are worth a shot. Aiptasia X, F-Aiptasia, and use a homemade mix kalk paste. Look into all of these and decide what you want to try.
Peppermint shrimp, filefish, and Berghia nudibranchs, get some and don't feed the tank anything and you your liverock will get cleaned. It can take time, but these can be kept in control.
If you have wrasse, the Shrimp and nudibranchs are probably not a great alternative. If you have a lionfish, shrimp and filefish are probably not a good alternative.
If all you have is live rock, I'd go with the nudibranchs, or shrimp, or filefish (in that order) or get whatever one is easiest to acquire. Berghia are the only surefire predator, the filefish and Peppermint shrimp are good if you get the proper species.