Just one more thought on evaporation. Years ago we were also in the bird business - with about 4000 parakeets. We used a water cooler (swamp cooler, evaporator cooler - not sure exactly what they are called anymoor) to keep the bird house at a reasonable temp. Do not think it was ever very hot out there, even when outdoor temps broke 100.
Likewise I have worked in the chicken industry a bit. Not to get into details, but evaporative cooler are used to keep chicken houses (ones I worked with held up to 120,000 birds each) cool in Texas. The ones I worked with (construction at the time), had no windows, just forced air and micro mist.
Anyway, just thing with a little ingenuity evaporation could go a long way to keeping an aquarium cool.
58 gallon oceanic, Kessel 360 tun sun, pressurized co2, eheim pimp #179 - 2217 and diffuser