Some sort of egg? Who knows?

[Josh Hitchcock]

These are on the wall in the refugium. They are kind of a light pinkish color. The water in the fuge is about 14 inches deep and most of these are close to the surface. There are either 5 or 6 little legs sticking out from the center and attached to the acrylic. There are dozens of them.

 

[James M]

Medusa hydroids

 

[samnaz]

Medusa hydroids

+1

 

[KorD]

Agree with both above posts.