That article cause me to raise one of my three diffusers a foot or two off the bottom because of what you describe. We can get terribly hot in the summer, even at night, and warm the whole pond water up top to bottom with aeration.

A person wants MOST of the water stirred. Gives more area and resourses to the fish community. But from that article they need a refuge they can dip into and cool off.

When we used to scuba dive in the lakes in SW Missouri and NW Arkansas, in the heat of the summer fish would often be found right around the thermocline. I presume it is for the reason we are talking about. The upper water got warmer than they liked so they hung out where they could cool off easily.