Oi!
I think it is a peanut worm, it looks like the one that I had identified at RC a few weeks ago.
Supposedly they are very demanding on food, and if you have one that means that you have enough 'extra' food in the tank to keep it alive. Don't worry about the 'extra' food, as a worm it's harmless.
I left my 'example' in a jar for over two week with out circulation and when I thought it was time to 'get rid of it' I noticed that it was still alive so I put it into one of my 7 nano tanks, and it's still alive so they are heartier than most people think.
It's harmless, less so than bristle worms, so let it alone, it's just more 'diversity' in the tank.
Cheers!
nigle
!~!