I have a 400W ballast that i have been told will run any bulb. There is something you have to do to the ignitor. Take it out of the loop. This will make it run the MH bulbs no problem I have been told. I was also told to put in a switch this way both bulbs could be run if you needed to change the bulb type. Typical grow setup. Needing to change spectrums for growth & flowering stages.