well, how about using a blacklight behind your regular lights, or just in a 6 hour night? if it filters out harmful UV rays and allows the beneficial UV rays to pass through, then it should be pretty good as a supplement...but yeah i totally know they need bright white light most of the time; cool white flourescents for vegging and warm or soft flourescents for flowering will simulate the metal halide and hps situation, with less lumens of course