You should have a set time that the lights are on and the rest of the time the lights should remain off. The lights do not need to be on for 10-12 hours unless you have a planed tank with live plants. If the tank is decorated with fake plants and decor you can have them on for a set time each day. For example, in a tank that is not planted you can set a timer to go on at 4pm and turn off at midnight. If it is planted you can have the timer set to turn on at 2pm and turn off at midnight. This will give you plenty of time to view the tank when the lights are on and the fish will have a set time where it is daylight in their tank and lights out or nighttime the rest of the time. Your fish will be happier this way and so will you. Keeping the lights on all of the time is also a recipe to have a severe algae breakout even if you do all of the water changes and regular maintenance. Timers are relatively inexpensive and will keep your tank on track with a regular schedule.
Marinemom