Strange worm on Goniopora

[PurplePolyp]

I spotted this guy a little while back and never got a photo but he finally showed up again. He is always seen with the Goniopora. He never travels anywhere else and can usually only be seen when the flowers retract.

 

[AbsoluteFaye]

I just tried looking it up for you and it seems like a lot of people have those! On that specific coral. But I'm not finding any info as to what it is. Sorry. Hope someone else knows! Looks weird.