Cyano or coraline?

[EQCM2B]

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 becuse it is to dark to see with the camera. Could this be coraline?

Any suggestions welcome.

Thanks,
Steve

 

[Dubbin1]

If it is hard and does not come off then it is coraline. If it wipes right off then it could be cyno.

 

[crzy4reefs]

if you can' scrape it with your finger or wipe it off it's most likely coraline, i only scrape it with a razor on the front of my glass i leave it on the sides and backs