I agree with fans. If you have a sump put them there, if not, on the display will also work. Keep in mind that the idea is to cool the water. A lot of hobbiests attempt to cool the tank by lowering the temperature of the lights, that's not going to work. The cooling mechanism is evaporation so point the fans so that they blow drier air across the water surface and increase evaporation.
In my humble opinion, 79F is too cold for most tropical reef animals. I don't know what animals you're keeping so I'll leave it at that.