Don't leave your lights on for more than 12 hours a day. You probably only need to have them on for 8 hours if you don't have a lot of high light demanding plants.
Also too much light can grow extreme amounts of algae. So you will have to experiment and see how much light is best suited to your tank.
I use an electronic timer with my lights so that they turn on and off at the same time everyday
No more forgetting to turn the lights on or off