Not sure what this is

[ciodavid]

I have had these guys for about 5 years and got them on a live rock years ago. What are they? They are doing good, but they could be a pest for all I know. Someone told me it was a zooanthid but I don't know. Sorry the picture is awful, it was the morning and I haven't scraped algae in a while.

 

[ciodavid]

Is the picture working for everyone? This is my first time posting on here so ill try putting the picture on there again. I'm using tapatalk so maybe it will work better if I use it to post the pic. Thanks to everyone for your help!