Fans are helpful at reducing temperature when placed inside your tank hood. You can choose to purchase fans commercially or fit your tank with fans liberated from an old computer. Alternatively, you can remove a portion of your tank hood and aim a fan onto the surface of your water. Be sure to cover your tank with a net to keep acrobatic fish from jumping out and be aware that your water will evaporate more quickly.
If you house your pumps in an enclosed stand under your tank, it will also raise the temperature of your water through the bottom of the tank. Fix this by opening up the stand door and placing a fan so it circulates the air underneath the tank. The most sure way of cooling a tank and the best way to prevent fluctuations (unfortunately, also the most expensive) is to purchase a chiller.