HPS gives off the red- that's what you should be using for flower- for veg, use MH or blue-spectrum flouros
stinkyattic Reviewed by stinkyattic on . BULB CHANGE FOR FLOWERING.?? is it right to change your bulb for one that gives off more red and blue rays for flowering or js stick with ur HPS 400 all the way throw.. would respect the info THX.... :thumbsup::) Rating: 5