"Do you treat it like living soil regarding nutrients and ph?"
Great question Sticky, the strangest part of all is that the best soil for the air-pot up top is basically coco, nute-free ProMix plus lots of perlite??? The Dry Side upper root system up top is all about AIR, unfettered oxygen to help roots do what roots do. (super soil mixes just get muddy and wrong in octos)
It just works.
[Edit, oh yeah, pH is a big deal and wants to be 5.5 to 6.0 for feed water. If you are serious, you want to monitor pH, EC (or PPM), and the rate your plants are drinkng. If you know that you can adjust as needed for each strain's preferences.]