What is this: clear tubes

[MaJuBo]

New build but the live rock in question was in my prior fish-only tank for 18 months and this wasn’t on it at that time. I’ve not introduced anything new except the sand bed. So, I think this is algae? The rock does also have some sand on it. Green hair algae, a red tree-like algae(?), and these clear tube things. Any ideas?

The snails also came from my 18-month tank.

I don’t know parameters other than pH which is low (7.3….I’m working on it) and ammonia is 0.009 ppm (Seneye)

 

[JGT]

Looks like tubular sponges.

 

[MaJuBo]

Here are a few more photos. The tubes are flexible, dancing with the current, and are now on multiple rocks. I’ll try to post a video

 

[MaJuBo]

Video

 

[EeyoreIsMySpiritAnimal]

Sponge

 

[doubleshot00]

Sponges. I have them all over my nano.