I have a freshwater aquarium, and I use Lights of America Mini Fluorescent Aquarium Bulbs in the light that sits on top of the tank. The light takes two bulbs, and these mini fluorescents are a good buy. Walmart has them for a cheaper price than I have seen in other stores.
Each bulb is 10 watts and is made especially for freshwater aquariums. One bulb provides natural 6500k daylight and gives 40% more light. The model I use is 2110AQ. These bulbs are color enhancing, accentuating the colors in your fish. They are full-spectrum, have high-intensity output, make the water sparkle, and fit all aquarium hoods that use incandescent bulbs.
The mini fluorescent bulbs have also given me good service, partly due to the fact that I only keep the light on for a certain amount of time during the day, which extends the life of the bulb and gives the fish a chance to relax and rest. One mini fluorescent outlasts three regular aquarium bulbs (or so it states on the back of the box, but I can't say they're wrong).
For freshwater fish aquariums, mini fluorescent bulbs work just fine for me.