Can you identify sand covered tube with tentacle?

[renouart]

Sorry, no picture, but about a month ago, a tube started growing along the top of the sandbed out from the rock, and it was coated with sand, as if glued to it. I noticed that a single white tentacle would come out of the tube, apparently looking for food. The tentacle itself was about 2 inches long. The tube is now about 3-4 inches long, and about 1/8 in in diameter. Any thoughts to what it is, and should I be happy or concerned?
Thanks.

[Sk8r]

vermetid. Mild pest, food thief, but no problem unless in huge numbers.

[Misled]

I agree with Sk8r look here

[reefergeorge]

Nice picture.
I have never seen a 3-4 inch long vermetid snail. I didn't know they go that big. Most of mine are under half inch. A picture would help a lot.

[renouart]

That is not what the animal I have looks like, though perhaps just a different variety? The tube does not move, only the white tentacle that comes out of it. And the tube lays on top of the sand bed, not sticking out above it. I have those stringy things that are in this picture, but this tube is not the source of it, so I think maybe mine is different?

[Misled]

I have a couple that size in my tank. They don't bother much , but one was bugging my Fugi leather so I broke it off. Trouble is they can run back into a rock or the sand.

[dsn112]

I noticed exactly what your describing today. Mine looks like yours sounds. I caught it with its tentacle fully extended and then it went away. It is less then half an inch or so, but doesnt' look like the picture above,

[renouart]

looks like a spionid, I think.

[Paintbug]

check out the Phyllochaetopterus sp. here.
http://reefkeeping.com/issues/2003-05/rs/index.php
it is toward the bottom.