That was going to be my next suggestion. Go to Bunnings or a lighting store and look for LED spotlights. Bunnings does a 80w LED floodlight for about $120.00. A couple of those above the tank would provide a lot of light.
You can also use lower wattage spotlights like the one below but they might need brighter globes. Fortunately you can buy a higher wattage globe to go in them if required. The one in the link below comes with a clamp and you can make up a frame to clip it onto. The other light will also need a frame to support it above the tank. You would probably need two of the 80w lights or three of four of the 15w floodlights. It would be a matter of putting them above the tank and seeing if you get any shadows on the bottom of the tank.
If you get a few spotlights you can put them on a timer and have one come on, then an hour later the other can come on. At night you reverse that so one goes off and an hour later another goes off.
The other option, which is expensive is a Fluval 3.0 aquarium light. They are good light units but expensive.
