Noticed this last night. Pictures turned out terrible, showed up better in video. EDIT: click on the first two for animated gif if they appear static on your screen.
Their tentacles have a structure similar to spirorbid worms. Except it's way bigger than any of them but still very small, maybe 1/4 inch wide? Not seeing a tube, seems to exit directly from inside rock. It looks like what you may imagine out of a cross of spirorbid and a "fluffy" feather duster. It's mostly white/pale with a just barely discernible grey banded pattern. Unsure if neutral or a potential pest best dealt with ASAP?
Their tentacles have a structure similar to spirorbid worms. Except it's way bigger than any of them but still very small, maybe 1/4 inch wide? Not seeing a tube, seems to exit directly from inside rock. It looks like what you may imagine out of a cross of spirorbid and a "fluffy" feather duster. It's mostly white/pale with a just barely discernible grey banded pattern. Unsure if neutral or a potential pest best dealt with ASAP?