Tube Worm?

[kilr95ss]

Bought some coraline covered rock and noticed these tube looking things and every now or then, they appear to have a web coming out.

 

[joy13]

I think it might be actually a snail
Snails That Worm Their Way Into Tanks by Ronald L. Shimek, Ph.D. - Reefkeeping.com

 

[kilr95ss]

I think that might be it, thanks!

 

[joy13]

I only have a few and they haven't over run my tank so I just let them be.

 

[rdnelson99]

I have one in my tank as well and was told it wouldn't hurt anything so I left it.

 

[kilr95ss]

Gonna leave them alone then, thanks for the input.

 

[MBliss81]

It's a vermitid snail. I had one in my tank, too. They are common hitchhikers. They put out what looks like a spider-web like string that can irritate corals if they are too close. Other than that they are harmless.