I agree with Steve then sodium lights would be too yellow and grow bulbs likely don't have the correct spectrum.<BR>
Woody do some research before buying "just any" MH bulb for it, make sure you match the ballast to the bulb. Also check probe start/ pulse start bulb requirements for it. The incorrect one may start and run but then burn out, blow-up or even may cause a fire! That sounds scary, but it's not that hard to narrow down the correct type bulbs that unit could use and avoid problems that might occur. Keep in mind if your new to MH use that they do run hot, both to the touch and to the tank, so watch the tank temp the first day or so. Lots of people have "old" bulbs here on RC, that's a good way to test & see what bulbs/color you like (assuming they are the right type) and also allows the intensity to be a little lower to start. You could probably get someones old bulb to test with cheap or free if you ask.