Gti_Leo
Aquarium Advice Addict
When you dive on the real thing and do a lot of photography, as I did, you realize quickly that almost everything but blue light penetrates much deeper than 30'. But some corals, like zoas are in tidal zones and can be under very little or no water for short periods of time. Those get hit by a lot of UV and it would have some effect on protective pigments. And UV penetrates water pretty well.
But growth comes from primarily blue frequencies because that's what they evolved to absorb in the wild. Not that they can't grow under other colors.
blue green yeah whoch is why we use royal blue or actinic supplement lamps. some SPS may benefit from a bit of full spectrum as they are higher up in the reefs and more full spectrum gets to them but to stimulate zooxanthellae algae growth its in the wavelength of 420-480nm