I'm using only big cfls. I have 4 x 200w cfls. 2 are red spectrum 2 are blue. Only using 1 blue for the 2 plants growing atm, less than 2 weeks old but thriving at the moment. These lights are huge by the way, I don't know if I can fit all 4 in, but I have a 400w grolux hps thing if I need it.