Originally Posted by AquaRick
Keeping fans on your tank surface will only "cool" the tank down to the ambient temperature in the room. Unless your room is always cooler than 81, it won't do much in the long run.
"The principle underlying evaporative cooling is the fact that water must have heat applied to it to change from a liquid to a vapor. When evaporation occurs, this heat is taken from the water that remains in the liquid state, resulting in a cooler liquid."
It is possible for the tank to get several degrees cooler than the room temperature. My tank stays between 76-78 room temp is 78-80 and I only run the fan 15 minutes out of the hour. If I were to run it full time the tank would stay between 72-74.
I agree there is nothing wrong with 81 degrees provided its stable.