Need ID on sand tube

[Ursus]

Noticed this for the first time last night. Have looked around the web but can't seem to find anything like it.

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When I spotted it last night the part coming down from the rock was not touching the sand. Over night it constructed the two side pieces making it an upside-down Y.

 

[papagimp]

I'm not entirely sure what those are but I have oodles of them myself, I swear i've seen a feather duster come out of one, but in some of the others i have these funny clear/white thin wormy things that stick out.

 

[NCreefwannabe]

some are feather dusters. some are worms ( i forget their name) and sometimes, i had those, but they werent tubes, only they looked like them. and came from my snails going from the sand to the glass. leaving ooze aand sand marks at the very bottom lol.

 

[Ursus]

I added a small colony of GSP to my tank about a month ago and noticed a clear tube on one side of it. At first I thought it was a part of the GSP, but now I see that the GSP is growing over the tube. Nothing has ever stuck out of it, but perhaps whatever was in it is making itself a new home.

Also, on the underside of the GSP I can see several single polyp arms of some sort. They are clear and have five or six arms each. They must be filter feeders of some sort as they are recieving zero to little light but I can see food inside them. With the camera I have, I doubt I can get a picture. They are impossible to see with out a flashlight.

 

[Paintbug]

the ones pic'd here look like Chaetopterid or Spionid worms. but they could be a couple of other thing, none of which are harmful.
http://www.melevsreef.com/id/dualpalps.html

 

[gman19]

I have tons of them in my sandbed. They are some type worm in my case as one can see 2 tentacle type things sticking out about an inch and a half or so.

Pretty cool...I figure (and hope) they are harmless.