Feathery cirri, spotted palps

A few weeks ago, I noticed that several of the hermit crabs in my tank had paired up, with bigger males hauling around their chosen girlfriends. So this week, I've been examining all the larger females, looking to see if they are carrying eggs. It seems to be too early to be sure; there are a couple of maybes.

Meanwhile, I took photos of several of the other tank residents. Here are two of the large thatched acorn barnacles, trolling for plankton.

The thatched acorn barnacle has black cirri.

This one houses several worms in its shell.

These tiny three-sectioned tubeworms show up in the sand, and in many of the assorted shells in the tank, including in those occupied by hermit crabs. In the sand, up against the glass wall, I can see the tiny worm; otherwise, all that I see are these two long palps. I don't know if the spots - I've never noticed them on other worms - are bits of material the worm is rejecting, or actual palp markings. I'll be watching for them in future.