I have read several reports that Oscars don't like a lot of light, and they don't like bright light. I took out 1 of the two fluorescent lights in my canopy so it would be less bright. Now I am curious as to how long is optimal to leave them on. The light is on a timer, so it can be adjusted to any length. I have it on 12 hours right now 8-8.

I think that each fish is individual and some fish may be a little more timid and skittish than others. Many waters in the Amazon region are very murky & dimly lit so if you are keeping fish from that region they don't require tanks that are very brightly lit. In the tropics I think something like 12 hours of daylight so there is nothing wrong with leaving the lights on for that long. However, I tend to put mine on for a few hours in the evening.

i believe it will depends on owner's preference. some people have it on while they
are still awake...just to see the fishes ... and shut it off before sleeping.

oscar need sometime in darkness specially while sleeping...although they could
also sleep while light is on. so it is up to your choice....

good question!

well the fish can see just fine without any lights at all in the tank, ambient lighting from the room is generally enough so having lights on your tank is completly optional, provided of course you dont have live plants, and most oscar keepers dont due to the oscars nature of destroying said plants... if you have plants you need to keep the light on however many hours a day is best for them. i dont think the fish care either way.

is it ok to have the lights on for various times? for example, I usually just have the lights on in the evenings when I'm home to enjoy them - if I'm not home at night, i don't turn the lights on. There is ambient light so they're not in total darkness. Weekends the lights could be on for 12 hours or so. Is it ok to have the lights on sporatically - i.e. no schedule?? or is it better to have a set schedule (with timers)

in the wild, there is no light schedule during flooding that make the river
bottom dark at all times, thus, i think there is no problem on erratic lighting
schedule. i am actually switching the light at my availability irregardless of
time.