ID Please

[nojinnyc]

What is this thick purple/brown algae?

 

[RareEarthCorals]

Cyano... Redish brown comes off in sheets. The scourge of every reef tank!

 

[nojinnyc]

It doesn't come of. Even with scrubbing!

 

[RareEarthCorals]

Ya its a bit harder to come off the rocks. You have to scrub it off with a wire brush. Do you have it in other areas? Can you take picture using natural lighting? Almost certain its Cyano.