Identify this anyone

[Nezzwilson]

I've just bought a tank off someone and was wondering what this is. I've looked it up on net and closest thing I can see is feather duster worm but it is mor like an egg shape. Anyone with ideas I'd appreciate it. Cheers

 

[Mebbid]

As much as I can see it looks like a feather duster. Does it retract when you touch it?

 

[Sniperhank]

Still looks like the cap of a feather duster. If there is still one in the tank, they expelled the cap when stressed. That is if it is still around/alive. You'd see a worm crawling around if it was still there or the tube it lives in.