Bill - turned the diffuser on around sunset and let it run all night. Just got off the water and could not find a temperature difference between top and bottom of more than 2 degrees. Figure I will leave if off for awhile and check it regularly to see how quickly that changes.
By the way, have had several relatively cool mornings for us the last few days, morning low of 57 this morning for example, so the surface water temp had dropped to 76. I am sure it will be back around 80 this afternoon with full sun but that would still be within the 5 degree range you recommend.
Appreciate the advice. Will let you know how the temperature changes in the days ahead.
Dick
