Live Rock - White stringy tentacles

[rglenn828]

I just purchased live rock from a LFS that is from the Gulf of Mexico. The rock has white stringy tentacles that come out from the rock mostly when the light is off. The tentacles are as thin as a human hair and last night actually grabbed a small piece of silversides and pulled to rock. What are these? Should I be concerned?

 

[larouche10]

Not sure what they are, but I have had them too. They will not harm anything. Nothing to worry about....

 

[shel]

I don't know what they are, but I currently have them. They don't seem to be a problem. Mine also mainly come out at night and some of these "Things" are 1/2 to 1 inch long.