Pod Chutes?

[AK77]

Hi all,

I saw these structures appear at the front of my tank about 2 days ago. I just had a close look at them and it seems to have been made by amphipods of some kind. If you look closely, you can see the little things in there.

I have them running all over my sand too.

 

[TigerIssey]

I have some in my sump.

 

[Buddyboy67]

those look like abandoned spinoid worm tubes...pods will congregate around these for shelter