it all depends on your ballast. if it has a switch on it that says hps/mh then yes you can run regular hps/mh bulbs in it with the switch set to the correct position. if theres no switch then you have to get a conversion bulb. i run a 250w switchable sun system 2 fixture and it can run both with regular bulbs. http://www.sunlightsupply.com/p-12578-sun-system-2-fixtures.aspx