Lightingpart of "A Rich Person's Guide to Aquariums" by Philip Greenspun
A fish-only aquarium requires minimal attention to lighting. You want a timer from Radio Shack to turn the lights on and off every day. Tropical fish should get 10-12 hours of light. There is no reason to get an especially bright light because you'll mostly succeed in growing algae. Standard aquarium lights are cheap fluorescents with non-electronic ballasts. These work fine but after a year the bulb has faded (fix with new bulb) and the ballast has standard to make an annoying buzzing sound (fix by throwing out fixture). It is probably best to use a more expensive compact fluorescent fixture, which will include an electronic ballast that won't buzz. If you have a 48"-wide, 55-gallon tank you won't need a 48" wide compact fluorescent strip. A 30" or 36" light will provide more than ample illumination and reasonable uniformity.
A planted freshwater aquarium requires brighter lights, traditionally at least 1-2 watts per gallon. The All-Glass compact fluorescent striplights are probably a good place to start. Get a clear glass hood for your tank so that you can drop a second striplight on top if necessary.
A saltwater reef tank requires ridiculously bright lights, ideally metal
halide. Of course these generate a prodigious amount of heat as well,
thus necessitating noisy cooling fans.