Maybe a large spionid worm? I am not sure if this is correct, but the picture linked looks pretty similar.
Before this search, though, I thought spionid worms were much smaller. In my FOWLR, they are tiny compared to what yours looks like. There are many pin-head-sized white curly tubes in many locations in my aquarium.
It also may be a chaetoperid worm. It appears that these are larger than the typical tiny spionid worms.
Similiar to a spinoid, this teribellid has a tube longer than the spinoid. Spinoid and terrebillis are both harmless but can be a nuisance. If you with to remove at the base, not center as it will simply rebuild its tube