The geothermal pond loop and closed loop chilling system for a pool will both add heat to the pond water as will any aeration system you add. So, to keep the pond as cool as possible, forgo the aeration system or at least only do surface aeration, such as, fountains with a shallow intake. I am not saying that bottom diffused aeration would ruin your residential systems, but a bottom (or near bottom) aeration system will change the lower water temps during the summer and you will lose some efficiency. If aesthetics are your main concern, a shallow fountain or fountains will effect the ponds temps alot less especially down where your geothermal lines are.

I'm not experienced with geothermal systems, but I can give you bit of info to explore with a geothermal expert of your choice...

My 1/4 acre pond (10 foot deep) had bottom water temps of 70 degrees F before the bottom aeration was installed and started up (late May). Within one week of only running 12 hours at night, my bottom water was measuring 10 degrees higher. Bottom line, is that you could warm your lower water column by 10 degrees with an appropriately sized aeration system and that 10 degrees will effect the geothermal system's efficiency. Check with your expert to get an idea of what that would do to your wallet. SideNote: I, now, have my 3 diffusers set about 4 foot below the surface and still do not have any evidence of a thermocline. At least at my small, rather shallow, pond...a thermocline with aeration is a myth.

Fountains are very pretty to look at and, given you install enough of them, they can help alot with floaty stuff on the surface and help keep the water more reflective. And, you can run them when you want/need as opposed to bottom aeration that needs to be run on a regular schedule.

My 2 cents, Welcome from West Central MO!

Fish on!,
Noel