Not with hydro... You don't get stem rot with hydro.... Unless you're doing something REALLY stupid.... The whole "highly oxygenated water" and cooler temperatures part helps eliminates root rot, which would also eliminate chances for stem rot...
If you think this is a recipe for stem rot, then how the ferk do you think things grow in Aeroponics?
Stem rot occurs when unoxygenated stagnant moisture stays in constant contact with the apical meristem.
(For those that don't know, apical meristem is the main stem.)
On top of that, the stems of pot plants, in dwc, sit ABOVE the water line in their net pots, in fact in my system the stem line is slightly above the top of the bucket... So no chance of stem rot, because water is NEVER in contact with the stem, EVER. You can't fill the bucket to the top anyway as displacement will push excessive water out. Not to mention the flood you will get when you turn the air on as the excess water bubbles out of the top of the net pot... Which I've done on several occasions over my 30+ years growing and NEVER got root rot.
On top of that, the main portion of the rootball, is where root rot occurs in DWC, if done right, the main portion of the rootball should be growing beneath the net pot, and be completely submerged in vigorously aerated water.
Between the bottom of the net pot, and the water level, is where root rot is likely to occur, as highly moist air and higher temps in that little air chamber will promote root rot when even the smallest amount of light is added. To prevent this, fill the water up in the bucket, so that it eliminates that chamber.
@jcommerce ; I am sure you have the best grow out there, for you. However, your way is not the only way, there are many people with decades of experience both in growing marijuana and other more legal operations that are full of sound advice, most of which you would probably claim would not be the way YOU would do things, and well, thats what works for YOU. Now have a nice day, doing, whatever it is you do.