Sand tubes

Hey guys. I bought a piece of live rock a couple of weeks ago and now I am starting to see these sand tubes appear on that rock. At this time they are limited to only one area of that rock and they were not on it when I bought it. The LFS had this particular piece of rock for a couple of weeks so I don't think what ever is building them is a hitchhiker. I say sand tubes becaus the material they are made out of looks exactly like my sand substrate and they also move with the current. Any idea exactly what they are or what is building them. Good or bad? I'd post a pic but the camera is missing the usb cord. Thanks.

 

They are most likely Eupolymnia crasscornis (spaghetti worm). They often build tubes from whatever they can reach from their burrow.

 

Thanks. Good or bad?

 

They're good. They will send out really small sweepers to catch uneaten food.

 

does it look similar to the ones i have in this thread

http://www.3reef.com/forums/id/3-easy-ones-44656.html