I find it hard to believe that actinics (or blue LEDs) would fail to grow plants or corals considering the chloryphyll-a pigment peaks at around 435nm, chlorophyll-b around 470n, and the combined photosynthesis of all pigments peaks at about 425nm (even higher than the peak in the warm spectrum). I built my own LED fixture with twelve 3W Cree LEDs peaking at 450nm along with six 3W 6500K and six 3W 10000K LEDs to put over my mainly softy tank. About a year ago, just to test out if the blues alone would grow anything, I ran them with the whites turned off for about two months. I actually got really good growth, especially in my zoanthids. I see no reason why this would be incomprehensible, and why this concept shouldn't be used with plants as well.