Will aeration increase or decrease evaporation in the summer?. I am thinking moving water interacts with air more readily but that cooler water coming up from the bottom will not evaporate as quickly. any thoughts?

I normally don't worry about it. If there's not enough O2 in the water, and fish don't have enough to survive, then how much water is a moot point.

If water is too warm, evaporation also cools the water.

I wasn't suggesting it should impact the decision as to whether to aerate or not, although if reducing the heat of the surface level water molecules would reduce evaporation, that would be a good thing. Certainly possible the impact is insignificant. Just curious and wondering whether anyone knew.

Cooler water will actually evaporate faster in warm/hot dry air, just as warm water freezes faster in cold air due to the temperature spread. The "boil" of bottom diffused air will cause cool water to evaporate faster.

The heat transfer rate is proportionally faster the wider the temperature differential is. The small bubbles of the diffused air that help lift water also provide a huge surface area for the heat to transfer rapidly.

I'm not convinced that warm water freezes faster than cold water. When a tray of warm water and 'cold' water are placed in the freezer the warm water tray can freeze faster, but this is due to the warmer water caused melting below it and tray makes better contact the freezer than the cold water tray.

Heat in water can be measured in calories. Heat calories have to be lost or removed for water to freeze. Warm water has more heat calories than colder water. Those heat calories have to be removed to the point the water freezes. The more heat calories there are the longer it takes to remove those calorie units and freezing occurs. The same principle should apply to water evaporation. See into in this link.
http://www.physlink.com/Education/AskExperts/ae7.cfm

Here is an interesting discussion on water evaporation:
https://van.physics.illinois.edu/qa/listing.php?id=1474
Cold water vs warm water evaporation
https://van.physics.illinois.edu/qa/listing.php?id=16382

with all things being equal, cold water will freeze faster. But throw near boiling water into freezing air, and being less dense, and having a wide temp differential, ice crystals form as the water falls. Toss cold water into the air, and it lands wet.

It comes down to the surface area, density, and the temperature differential.

Here is more info that reinforces Rainman's statement of warm freezing faster than cold. Water is a unique substance.
https://medium.com/the-physics-arxiv-blo...ct-d8a2f611e853