@Webb.Peter, cool. Are you saying just controlling temperature alone can create a specific amount of DO in the water? I find that hard to believe that controlling temperature just on its own would have such a dramatic effect, but i acknowledge my ignorance in this area. Though i can see it helping.
So it sounds like you indeed are controlling root temperature (water) separate from air temp. That’s good. I had read awhile back that most plants prefer their roots to be slightly cooler than their leaves. Sounds like you are keeping the roots at 20 C while your leaves are at about room temp (22-23 C). Most human pathogenic microorganisms grow at 37C (body temp), but this is not true for all and i would think certainly not true for many plant pathogens.
Controlling temp will help with many, but i imagine many others are adapted to cooler temps and will thrive in those temps quite well (i.e. 20 C), so i think investigating other pathogen reduction techniques to be worth the effort. Hence my mentioning of Microbial Antagonism. This is a technique that works well in humans, so why not in plants. Besides i know in soil plants often grow better when grown in non-sterile non-mono environments like with beneficial fungi as the fungal networks help plants gain more nutrients. Paul Stamets work also mentions crazy cool interesting things like how fungal networks can transmit pathogen data to other plants. For example when one tree is attacked by a certain bug the fungal networks can transmit that data over miles away and the other plants that have not been attacked show a response to the bug attack by emitting certain stress chemicals. But this is in soil, not water. Still cool though.
Though not pathogenic, a good example of this adaption to different temperatures can be seen in domesticated strains of Oyster Mushrooms. The white ones grow at 55–75 °F. The blue ones grow at 45–65 °F. . And the pink ones grow at 70–85 °F.
EDIT: i forgot to add that with aeroponic piezo-based misters that if you leave them on all the time they heat up the water quite a bit from all the vibration going on. So i imagine controlling water/root temps with those could be quite the challenge.