Thought it was algae...until it squirmed! ID help?

[csammis]

I was doing a water change on my Biocube last week and pulling out a bunch of unexpected caulerpa while I was at it. I saw a large green thing on the back of a rock and started to pull it off until it squirmed back from my fingers. Freaked me right out!


Terrible cell phone photo by Chris Sammis, on Flickr

It's attached to the rock and hasn't moved since I first saw it. It doesn't seem to have gotten any bigger or smaller or changed shape at all. Any thoughts? I could probably get a better shot of it if that'd help - this is just using my iPhone so I could get a thread posted

 

[saltyair]

Cucumber?

 

[Sugar Magnolia]

Cucumber?

That's what I was thinking.

 

[csammis]

Huh, really? I always thought cucumbers were generally more mobile than this is. It hasn't moved from that spot since i first noticed it (several weeks ago; I only tried to move it last week) and it seems to be anchored on the left in the picture I posted.

Assuming it is a cucumber should I just leave it alone or take it out?

 

[Sugar Magnolia]

Some cukes, like the filter feeding variety, tend to find a spot they like and stay there.

 

[pagojoe]

It looks Neomeris-like to me. Are you sure it isn't growing from there?

 

[robotman]

is that an aiptasia above it?

 

[Moort82]

Looks like a type of volonia algae and you have some hydroids above it.

 

[S13<3]

could be some kind of tube worm