Mystery worm? Is it good or bad?

[Steve-Ward.net]

Did a water change today, and in rearranging the rock work, discovered several of these long white looking things, with crowns.

 

They look kind of like feather dusters, except some have bright red crowns, and others are white.

 

The white crowns look similar to a couple small featherdusters I purchased over a month ago, but thought they had died in transport (never came out, over several days), so removed the stalks from the tank.

 

Is it possible the worms just left the stalks, hid under the rock and reproduced, or something?

 

Or is this something else entirely? It bears mentioning that whatever these things are, they were living on the underside of the LR until this afternoon, so it's something that doesn't need any light.

 

Thanks in advance.

[Acoustic]

I cannot say.......need better picture......must read next thread.