Cheap is good to a point, the K rating for the off the shelf halide bulbs at say Home Depot etc.. is usually 2600k or in about there. Waaaayyyy to yellow to be of use in a plant tank or anything other than an emergency light. For a daylight colour you can find hydroponics shops who sell 5000k to 6500k bulbs. A lot of people think they can use halogen work lights, because they are cheap but again the colour is completely wrong for anything water related other than generating heat and usually to much of that.

Doug

be careful with how much light you have over a planted aquarium. you need to ballance the following three things:

1. light
2. nitrate
3. CO2

if you increase the light but aren't dosing nitrate and carbon you'll have lots of algae. I'd say don't bother lighting it with MH unless you're willing to get into CO2 and nitrate dosing.