Can someone tell me what this is?

[Drndoc]

Can someone tell me what the white worm looking things on the live rock are. It's all over a couple live rocks but has not spread anywhere.

 

[scardall]

If what you are reefing to is behind the crab. Those are a type of feather duster tubes. you might see some after lights out. use a flashlight after tank has been dark for awhile. good luck

 

[Drndoc]

Are they bad for the tank?

 

[scardall]

Are they bad for the tank?

No, feather dusters are good for your tank as they are filter feeders. You can go to liveaquaria.com to find information on what some of what you have.