esshup, at what depth are you thinking of doing temp readings? I have a maple syrup thermometer but cannot immerse it. I guess that means I could get temps down to about 8" deep.
This time of year we don't have hot days anymore so I probably don't need aeration at all.
Last time I did calculation of how much the air bubbles lifted water and how deep my system was and what its CFM of air was it came out that I was just about at turning over my whole pond in 24 or 26 hours if I recall correctly.
But even if I'm turning over the whole pond, I still notice that there is definitely colder water deeper than say 5 feet (just by how cold it is when wading in to do maintenance)
The hardest part of finding a suitable thermometer is the cord length. I bought this cheap Chinese thermometer on Amazon. 10m cord. I marked the cord in 1 ft increments.
I compared the readings to a couple other thermometers I have, including a pretty nice stream thermometer for fly fishing. All thermometers were consistent over a wide range of temperatures.
https://www.amazon.com/gp/product/B096K1Z58S/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
