Thanks everyone.
[MENTION=38412]mcgyvr[/MENTION], when you say "green rock", are you referring to the green hair algae that's slightly visible, or the green tint on the rock itself?
I'm definitely addressing the GHA (a long and hard fight, but I'm winning).
If you mean the green tint on the rock, I didn't even realize it's something I should be concerned about. I can confirm that most of the rock has a light green covering on it, and that it's the only rock in the tank with that color. Plenty of purplish coraline elsewhere, but nothing green.