Is this something bad? I was wondering if it was from phyto plankton. I was using some old phyto(7 weeks old, still green, not stinky) and this green stuff started arriving. I am not sure if it is just the old phyto settling on the rocks. I tried to vaccuum it up, but it didn't come off the rock. The arrows point to the color that best represents the color of the culprit in the aquarium. The darker spots are shadows my camera picked up from the angle of the lights. I don't know what green coraline algae looks like, so, maybe that is what it is. Any ideas?
