Yes, no more than 12 inches for a 400w is ok, the closer the better (keeping temp. in mind) because of the fact that the lumens are exponentially diminishing.
BigNugs4U Reviewed by BigNugs4U on . HPS I finally got an HPS on it's way!!! I'm real excited as I haven't even put my plants into flower yet. It's a 400w Hps w/ a reflector and ballast. My question is how far should I keep it from my plants (when it gets here!!), and secondly are all HPS bulbs in the red spectrum the plants need?? It comes w/ a bulb that supposedly puts out 52,000 lumens. I'm gonna supplement that w/ 1 150 red spectrum cfl, my 4ft Fluro tubes (think I'm gonna leave the cool whites in so there's some blue during Rating: 5