This is on a new tank setup but the rock was live when I put it in and I noticed a few of these guys attached to the rock. This one seems to be the largest and extends out a good bit at times. Excuse my noobness if its something very common but I'm new to the hobby. Thanks!
It looks like aptasia , if it is you need to kill it immediately. It spreads real fast and they sting any corals it touches. You can make up some Kali paste and use that to kill them.
Looks Looks to be majano. Thing wit ap x is you have to get them to eat it. If u can pull rock out inject it with like juice or vinegar . Or like I do now Let the rock sit out for the day
