Tanks that are 36 inches high need 250watt spot lights to penetrate the water depth.
If you have 2 or possibly 3 spotlights you could spread them out across the top and hang them about 12 inches above the tank. I know you would prefer to rest them on the tank but most spotlights are designed to hang down. You might find a company that makes LED spotlights in a housing with wifi and built in timers, etc, but I don't know of any, altho I'm sure there are some out there. If you can put your location in area under your name, then people that live in your country might have more idea.
If you have individual spotlights you can put them on timers and have one light come on, then an hour later another comes on and an hour later the third one comes on. Then in the afternoon/ at night, you have one go off, then an hour later another goes off, and an hour after that the last one goes off. This would simulate sunrise to sunset and the tank would have some light on one side first thing in the morning and then at night the last light to go out would be at the opposite end.
Having the lights come on over a period of time is better for the fish because they won't be in a dark tank that suddenly gets heaps of light. It will be more gradual and less stressful.
Try to get globes with a 6500K (K is for Kelvin) rating. Don't bother going higher than 6500K and don't get anything lower than 4500K. If it's a choice of 4500K or 6500K, go with the 6500K.
Check your local hardware and lighting stores. LED spotlights are quite cheap and readily available from most of these places.
