Who are these guys?

[mmcdade]

We have had a bunch of these guys (maybe 2 or 3 different things?) for weeks. They are in the sump and on the DT walls and when we clean the walls, they are back in three days or less. Any idea what they are, if they are harmful and what to do about them? The DT is 140 gallons, fish and a little soft coral. Only about 4 months since fish went in. Obviously, we are new to this...

In the photo and video, the scale lines are 200um apart (1/5 of a millimeter).

TIA!

-mm

Sidewall of sump.

White, chalky, larger and not apparently alive.

 

[The_Paradox]

I’ve seen Spirorbis look that if they were damaged. Might be worth a google to see if that’s what they look like in your tank.

 

[ISpeakForTheSeas]

This pic is probably of a broken Spirorbid worm tube (they’re harmless filter feeders).

The crawling things in this video are probably ostracods (seed shrimp) - harmless “pods” for your tank. The wheel-shaped thing next to them is interesting; I’m not sure what it is, but there are a number of things it could be.