So I wanna say this is green coralline but I could be wrong. It’s neon green only growing on my live rock. Now I have taken a toothbrush to it and it doesn’t come off for the life of me. It just kinda popped up and shortly after I started getting purple and pink coralline growing on the rock also. I would think any other kind of algae would come off easy??? When I googled it the pictures pretty much look the same.