Help identify what is on my live rock

[spenceski23]

Could some help me identify what these white stringy worms are that collect sand to made a little tube?
Also circled in the photo are these duster looking things. When you get close to it they quickly shoot back into a tiny little hole in the rock.

 

[Goaway]

Hair worms and feather worms. Harmless and benifical to reef tanks. Filter feeders and detrivores.

 

[SnazzyUrchin792]

I have those everywhere. Completely harmless.