I tend to use overhead lights in the room (four low wattage flourescent blubs) to provide light for the fish to see by. I leave the over tank lights off most the time and keep low-light plants.
You can get T-5 shop lights now, and they are more efficient than T-12 or T-8.... but 20 shoplights running 10 hours a day adds up no matter how low the wattage is.
The latest installment of the fish room series is up. Enjoy!