This is great! Looks like a Troll...Nice try, but my Urchin begs to differ, when you have an Urchin with a GHA Mohawk then it's bad.
My only experience led me to take drastic measures, 7 weeks of dosing Vibrant, 4 weeks of dosing Hydrogen peroxide and vacuuming everyday while watching my phosphates.
Into the 5th week the GHA started to lose its grip on the rocks, I vacuumed everyday for the entire time, towards the last few weeks the GHA was just sloughing off the rocks.
I have been clean for two months, no signs of GHA.