Hard to tell from the image but.... do they swirl on the flat surface of the rock (like an ear laid sideways)? Do they poke out of a volcano shaped tube? How big are they?
I think they are just a type of feather duster commonly seen in new tanks... I have populations of them that have gotten rather large in hidden areas in my butterfly-less sump... great filter feeders.
bope its not those, i have tons of those in my sump. im not sure what these are, they dont really look like feather dusters, nor have i seen the worm come out yet if thats what it is.
It looks like siphon tubes on a sponge. I have seen those yellow-green sponges that have siphons that look like that. Maybe one is inside that rock and has grown to stick it siphon and intakes through the holes in the rock?
