The above light you can find at most hardware stores and is perfect for hoods that are made for incondecent bulbs Usually 10g hoods. They fit a convention light bulb socket and are used more commonly to save power. I dont know how much is too much light and what spectrum of light they give off- but my tank looks great and my plant grows better than ever. I bought mine at Canadian Tire for $5 Can. each. They also last much much longer than incondecents.
BE CAREFUL TO GET THE RIGHT ONES!!!
you must get the ones that are small enough to fit without bending anything.
Don't get any with a wattage over 15w as it could be a much too bright or maybe even a fire hazard (although probably not)
The brand I have is called MINIMAX florecent spiral 13w