Suphew, I didn't mention the salties at all, or infer what you are saying.
I relize about the heat dispersion for lights as I do it myself. But if the ambient temp is 30 then a fan is just moving 30o air around.
In fact thinking about it, it may even warm the water up a bit more.
But if you want to go for evaporation to cool down the temp.
Drape the tank with damp towels, these evaporaing causes the inside temp. to drop.
Remember the old canvas water bottles?
Guess not, not many would now.
That is how they produced drinkable water, temp. wise.
Alan 104