Strange living thing in my tank...

[prophecyfactor]

I just started my tank a couple of months ago. The other night, I noticed a long blue string on my rocks. It looked to be coming out of one of the rocks, and had stretched itself almost 5 inches to another rock. It looked liked it had little eyes, almost like a crab or snail. When I turned the lights on, it pulled itself back into the hole in the rock. Didn't move really fast, but didn't take it's time either. I was wondering if anyone had an idea as to what this could be. I've asked several pet shops and specialty stores, but no one has any idea. Thanks!

 

[prophecyfactor]

Here's a picture (only comes out at night)

 

[mboswell1982]

what in the name of all thats holy is that thing?

 

[rotarymagic]

its called live rock for a reason... there's lots of life in it lol.

 

[sickboy]

About 5 inches you say? I have a worm (spoinid worm, I think) that stretches itself out. But it has two arms and I can see the tube that it originates from. I don't know if this is it, but you could look it up.

 

[prophecyfactor]

I think you may be right - I found a website using the name you suggested and there's a picture that looks pretty close - Excerpt: "...spionids are somewhat rare in reef tanks. They may make an appearance by extending their paired tentacles from a small hole in a piece of reef rock...". Thanks for the help!
Reference:
http://reefkeeping.com/issues/2003-05/rs/index.php
Figure 9

 

[yearofthenick]

Look for Cranberry, she has information on pretty much every hitchhiker. I think you can PM her if you find her.

 

[cranberry]

Woof! You give me too much credit.
If I had to take a stab at it I would have to say a spaghetti worm. They can have that blueish like colour. I've just never know a spionid to look like that and stretch quite like that.... it just looks different to me. A spaghetti worm can have only one extended arm. When I first found mine he was a single tentacle kind of guy.... but more arms came in time. Spaghettis can also be found in rocks like that.
So I would have to vote terebellid.... but I'm not sure on this one.
When you say head, there's nothing really there, is there?

 

[joebob7]

I have a few worms that look like that. They stretch when moving but sometimes just hang out of holes in the rock. They only come out at night as well, i was told that they were peanut worms. I have'nt had any trouble with them hurting livestock though so i assume they are safe.