Hi,
Phosphates and nitrates are needed to feed the GHA, if you keep it under control, the GHA should go away completely. It does look much better....
Algae (not just GHA, but any algae, which is a natural thing in a reef) will choke it out and it won't be able to bloom, then it will starve. It isn't in a good place if it's under the lights, it needs to be moved to a darker place in the tank, under a ledge or build a cave. It must be getting enough flow because it is blooming and seems happy in that spot. The coral itself doesn't care if it's under the light or not, it's non-photosynthetic... algae is it's enemy.