Hey .. I um .. I also sometimes call it "brillo pad algae" when in mixed company ...
I forget the exact latin name .. it is something like
Chaetomorpha linum ... I think most people just say "
C. linum"
I'll try to look up the correct name and edit this post if it turns out I got the genus name wrong.
(Edit: I did get it wrong. It is "Chaetomorpha" not "cyanaria").