I might be pointing out the obvious here so feel free to slap me if need be but you guys DO realize that MH
lighting falls into the HID
family of lights and that it's spectrum is IDEAL for vegatative plants.... Rite? I grow some of my own herbs indoors and use MH
lighting for this... I have never even seen a saltwater aquarium in person (I'm trying to give you an idea of my experience).
Seeing as PC
lighting both give off a bluish spectrum favored by vegatative plants I don't think it has anything to do with the spectrum of lighting but rather the intensity of the light. Maybe that particular type of algae only grows under very intense light -which an MH
That's my .02 on the matter anyway.