This communal housing project turned up at the front wall of the aquarium the other day.
|4 (or more) jointed three-section tubeworms, Spiochaetopterus costarum, maybe|
Each worm has two tentacles, which he waves about, catching dinner. They often build their tubes in sand, but they do like broken snail shells. Even when they're occupied by a hermit crab, as in this video from 2011.
(YouTube used to run it properly; now it's taken to pasting text for only a second or two and leaving us with a blank screen for another 6. I think I'll have to re-make the video.)
I'm busy with some other mini-critters from the tank, which I may turn into a video, if they co-operate. Tweet