It would still cool the water even if the ambient air temp is higher. If I can remember from my school days, evapouration is an Exothermic reaction.
I have about a 800L system, and a fan can drop the water temp by a good 2-4 deg C.
But yes, crutschow said, its a whole new topic.
Agreed.
The question is that: Will evaporative simple cooling suffice to reduce temperature to the desired value.
I use an evaporative cooler in my living room next to my chair consuming approximately 20l of water within 12 hours.
The air hitting my body is about 4 deg C below ambient temperature, which doesn't satisfy at all. (ambient temperature 46 deg C and fan outlet 42 deg C - still much too hot, wasting 80W of electric power + carrying water regularly to feed the machine). This device won't even change room temperature by 1/10 of a degree.
If the aquarium water surface is large compared with the surface of the basin that method might be reosonably efficient.
May be Crutschow is right saying it's a new topic, but I have experienced that very often the OP is directed to another approach to solve his problem.
Just some numbers using a cold mister rated 24VAC/1200mA. Initial temperature 32.7 deg C. With cold mist activated the water surface temperature dropped to 27 deg C within one minute (bowl content approximately 1 1/2l). To create a temperature drop of 5.7 deg C (by evaporative cooling) you need a fan causing waves on the aquarium water surface and I doubt a fancy CPU fan will be able to do that.
CPU fans are axial fans with low pressure and high volume. To create waves you need a radial type fan with high pressure at lower volume.
I certainly do not intend to talk anybody into anything, but these are the facts.
I go along with our Kaiser Wilhelm II who said: "Jeder soll nach seiner Facon glücklich werden." (Everybody should become happy his way.)
Cheers
Boncuk