Is this a sea cucumber?

Hey All,
This looks like a sea cucumber but I am not positive. It is about as fat and as long as my little finger and moved very slowly. It just appeared one day and I haven't seen it since??
If it is, does anyone know anything about its behaviour??
Sorry for the poor pics, but I had to reduce and reduce and reduce the quality to get it to upload, so lost quality.






Thanks heaps for your help ;D

 

It looks like it could be, but my cuc never very rarely leaves the sand bed, although has climbed the glass a couple of times when not happy.

Instead of reducing the picture, just crop it to the critter. Then reduce if needed.

 

If it's a cuke, it's likely a Cholochirus sp. as opposed to a Holothuria sp.. Cholochirus cukes do climb both the rockwork and the tank panes, and you'll see them pop out their gills to filter particulates from the water.

Holothuria, OTOH, are the cukes that sit on/in the sandbed. Tigertails belong to this genus.

FWIW, Cholochirus are the cukes that are rumored to nuke your tank if stressed or if they die in a stressful manner...