So I’ve gone through the diatom phase and am in the green algae phase. But now I’m starting to see these brown spots showing up on the dry rock. I’d like to mention that I do I have one small piece of live rock from my LFS that has coralline algae on it, though I don’t think that’s significant to this question. Any ideas on what it is? I have not tried brushing it off yet but by the looks of it, it doesn’t look like it would brush off. I’ll try that tomorrow morning when the lights are back on.