Putting aluminum foil behind the lights helps to make your lightbulbs more efficient, meaning more light is going to be focused into the aquarium as opposed to being scattered elsewhere. I wouldn't necessarily consider this a temporary fix, but it will help somewhat since your tank is deeper. There are really two things to consider with lights: spectrum (the Kelvin color temperature) and the intensity ( which you can measure with lumens outputted or LUX). I know purchasing light fixtures can be expensive so you may want to consider building your own flourescent fixtures. If you search youtube, you could probably find some videos on making DIY fixtures.
Hope this helps -
Hope this helps -