Critter ID growing in coral

[Mhamilton0911]

So I noticed this critter, looks like a fan worm, but it's invasively growing in the middle of a favia and also a chalice. I first noticed on the chalice a while ago, but thought it was a part of it? But then the new favia has the same thing, so now I think it's something else.

 

[CryptoNautical]

it appears to be a barnacle from the video.

 

[eggplantparrot]

barnacle

 

[Mhamilton0911]

it appears to be a barnacle from the video.

Is this harmful?

 

[mdb_talon]

Is this harmful?

Generally no. It can annoy coral and make them close up, but usually i just leave them