Can anyone tell me what this is?

[wgama]

A supposibly empty snail shell has long stringy white things coming out of it. They stretch themselves out to 6+ inches and retract when I shine the light on them.

[Chowder]

Spagetti worms.

[wgama]

That is what I thought Are they bad to have in your tank?

[KPG007]

No, they're fine. They will filter the sand a little bit.