All of the "best" bulbs are enhanced spectrum - adding more red to MH lights, and the enhanced HPS lights add more blue. Its growing obvious that both spectrums are the best choice for the plant. The light cycle itself triggers the flowering phase, not the spectrum of the light.

I'd like to see some studies that show that plants respond to HPS more than MH when flowering. I know its "a known fact" but then again so are hotspots from foil - but show me someone you actually know that has experienced it (burns from a wrinkle in the cabinet liner). Some of the old school growers I know only use MH lights, and produce some incredible nugs.
Tokudai Reviewed by Tokudai on . swapping out HPS 400w for MH while flowering.. I currently am in week 4 of flowering. I have read many times that running both MH and HPS at the same time is optimal for plant growth through the plant's entire cycle. I have a 400W HPS bulb running to emit the red spectrum right now that I was considering swapping out with my other metal hailide bulb that I started with during veg. My question is: would switching back to a metal hailide bulb at week 4 in flowering do more harm than good or could it possibly make the buds more compact? - Rating: 5