Easy man, I dont use CO2. Supposed to be good though. I have used 1x250w cfl 6500k for veg 2700k flower and 2x 26w cfl. big 250 blue for veg with 2x26w red and 250w red for flower and 2x26w blue. But its better to use more of the 26w bulbs so you can spread the light. Apparently the big 250w are not a economical as likw 10x 26w. Hope this help.