Fan worms/Feather dusters on live rock good or bad

[awong]

greeting everyone,
I got some feather dusters on my rocks and I would like to know if this is good thing or they are more of pets? any help or suggestion would really be appreciated. Thanks

 

[jcook54]

I actually love seeing them. There is a very small, thin, white type with a little tiny red feather duster at the end that can get annoying. I consider them "good" things to have but watch out grabbing a rock. They like to grow our of flow and if they've overgrown the bottom or back of a piece of live rock and you grab it, they can stick and stab your hand.