sand construction worm?

[dbowman5]

i have several of these things, i have trouble getting good pictures. this one has taken up residence in a shell. it has at least two tentacles. it uses them to pull in sand grains. gluing them? together into a tunnel.

what is it

 

[TriggerFinger]

Spinoid worms. They are cleaning up leftovers and waste. Good guys to have!

 

[dbowman5]

Spinoid worms. They are cleaning up leftovers and waste. Good guys to have!

thanks, i can find examples of it: Spionid worm