Fish have circadian rhythms just like us and their behavior can be influenced by the amount of light they receive. The fish in my Q-tank (located within a dark, enclosed tank stand) were lethargic and sluggish until I provided them with a light on a timer.
I would get an inexpensive timer (6 bucks at Home Depot). I have mine set to come on at 10AM and go off at 5PM year round. If I feel like watching the tanks when I get home, I just switch on the lights.
I agree that anything over 12 hours a day is inviting algae trouble.