ok, incandescent will not really be the best for plants - too much heat, too much energy - not enough light. does your hood use only one or two lightbulbs?
What I suggest: Go to a hardware store/ walmart/ home depot/ lowes and look for a CFL (Compact florescent) light bulb. If your tank has 2 bulbs then you want 2 CFL's of lower wattage (2 10 watt bulbs would be good) If it only has one bulb socket then get a higher wattage CFL (get a 20-26 watt bulb). Make sure the bulb is of 6500k - its usually right in the front of the package. These bulbs are usually labeled as "daylight" and cost $6-$10. I got a package containing 2, 26 watt bulbs for only $9 at my walmart. Here is an example of the bulb im talking about