you need to think about the water these fish live in while wild. its murky water so would be dark naturally. i dont think the oscars mind a bright light, i just dont think this is an issue. but i will say that 12-14 hrs must take an age to clean the algea in the tank? if you do get a lot of algea growth just put the tank on for about 5 hrs aday and this will help slow it down. if you have a good algea eater then leaving the light on may be feeding it quite well.
my own oscar tanks i only put the light on if im in there, if mates come round or im doing a water change. mostly its off al the time, its not a planted tank