Will cyano grow on the glass high up on the side of the tank? I have a dark red to purple, ( actually looks like dried blood), spot on the glass. It is not fluffy or anything. The Turbo snail went around it and now it looks like it is trying to flake off in one spot. Sorry I can't get a pic because it is to dark to see with the camera. Could this be Coraline?

Any suggestions welcome.

Thanks,
Steve