Why don't you hydro guys just use real O2[ not medical grade$$] and control the level in the res with controller?
Adding excess O2 to your water supply will raise the pH and thus a simple pH controller like fish heads use for CO2 will do?
I own both O2 and CO2 bottles and they are not a huge investment.
Then just make simple reactor to infuse it to the res?
The controller would note the changing pH[ O2 being used] and turn the tank on.
You need a regulator with solenoid also.
Sorry for asking stupid questions if that's what these are.
I have no clue if ferts would mess up such a controller?