I genuinely have no idea what this is. It's a circular-ish dark green/brown slimy looking patch growing on the rock. I don't see it anywhere else. While it is near the top of the tank it is in a shadowy spot. It doesn't look stringy like the brown slime algae I found in the algae identification files. I am at a loss. It looks almost like mold. Anyone have any idea what this is, how I get rid of it, and what risk does it pose/what problems does it indicate?. These are the best images I can get. It grows in a circular pattern, is not hard stuck to the surface like coraline, and I have no idea where my live rock originated.