Hello; You have to use a mh ballast with a mh bulb and a hps ballast with a hps bulb. The only way to put one in the other is to get a conversion bulb. Do a little research on the net and you can find out whats what; READ; READ; READ!
Gardenking Reviewed by Gardenking on . what lamp do i need for a 400w hps bulb? I've found a 400 watt hps bulb online that I want.. what kind of lamp do I need to plug it in to? Do I have to buy one of those expensive bulky reflectors or could I just find a cheap cord or lamp with an outlet I could screw the bulb in to, and then make my own reflector? -Dr. Nomad Rating: 5