I bought this LED light off amazon for a desk lamp (not for aquarium use)
Its plenty bright. I used to have a 13W florescent light in the lamp, and the LED light is a lot brighter, and a much better bulb for a desklamp because its directional. A flourescent (or incandescent light for that matter) is only as good as the reflector its mounted in, while the LED lamp doesn't use the reflector.
I highly recommend, and its only $9 with free shipping if you order $30 worth of stuff.
There's also bulbs at home improvement stores, but they'll be a little more expensive, and its harder to find 6000K or 6500K lights there.
You could also easily get away with a lower wattage bulb. Florescent lights need about 2-3 watts per gallon, but LEDs are typically more efficient, and in most cases you only really need about 1 watt per gallon. A 5W LED bulb is cheaper and will probably be plenty for your needs.
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