If you use really powerful lights, keep them off. If your heater is set below 85 which it obviously is i dont think it will make a difference, but i suppose you could turn it off.
If it gets any hotter, you may want to set up a "glacier run-off" system. basically just buy a big block of ice and raise it above the tank, and let it slowly melt into the tank, I would just put it on a tray and cut a hole and let the water drip down into the tank. But IDK the ice may melt to fast. If it does, wrap it in something that insulates like foam or even a blanket. Just an idea, i have never had to deal with something like that.
You could buy a small AC to put next to the tank but $$$$$.