Need help identifying

[sparkman2008]

As the title suggests I need help identifying this “stuff” that has appeared. I was away from home over the past couple days and when I got back last night it was there. It’s looks kind of leafy and is very thin but it’s growing from the coralline just not sure if it’s friend or foe. Sorry for the bad quality picture and thanks in advance

 

[blaxsun]

Maybe some kind of algae? It's really hard to tell.