Need help ID

[paullondon]

I noticed lots of red round spots on my tank's glass, some of them look like they have a little tail... what are this things?
I got a pretty accurate macro video here: https://youtu.be/IGXZMX-GWzo

[rssjsb]

You've got some hydroids there, so I'm wondering if they're related. Don't know anything about hydroid life cycle, though so maybe someone else will respond.

Those definitely look different from the pics on your other post, which did look like coralline algae.