ID on white worm ?

[adamfrer12]

I have these white worm looking things on my hammer coral. Also some on my live rock. What are they? Are they good ? If bad how can I get em out ?

 

[kacrocorals581]

just like your common feather duster, but these live in calcium tubes

 

[reefbeard]

Pileolaria sp. Feather duster. Not a bad critter but they do reproduce like mad in nutrient rich environement.