I have never seen this before. It almost looks like bubble algae. Has the same color and pops. But it doesn’t grow in clusters. It grows in individual pipes and sometimes even gets covered with coralline like the one behind the pictures arrow. This stuff grows like crazy on my algae scrubber screen and attaches to everything very firm. I have troubles scraping it off with a metal pick.
What is it? Is it some sort of bubble algae? What eats it? .