Please help me identify

[Jensworld]

Found this in a rock in my tank. Bristle worm?

 

[ndrwater]

Yup bristle worm.

 

[jaxredsoxfan]

Looks like a bristle worm to me but looks fatter than normal

 

[Jensworld]

Right I thought it was wider than the other bristles I have found

 

[Jay Z]

Piece of a bristle worm.

 

[rkpetersen]

They can contract and elongate their bodies; this one looks contracted, which is what they do when they're annoyed.