Feather duster on Duncan?

[ChromeSplat]

Hey, is this a feather duster? The white line like thing on the bottom of this Duncan? I see a small little black head pop out, and pop back in whenever I get close to the glass.

Is this harmful at all? Should I remove it? I never noticed this in any of the photos I have when I first got the coral.

 

[Rocks reef]

You can pull it out and scrape it off. It won't hurt anything

 

[Wallace11]

Hard to tell with this photo. Could be a feather duster (should see a small crown of feathers) which is harmless. Could also be a vermatid (brown/transparent tubes) - in this case I would seal the entrance with glue to kill it, or scrape it off.