there's obviously oxygen in the water or his plants would be dead. I think in heath's vertical grow that there is about 1" of water in the bottom of a 6" tube... or something like that. Which means that part of the roots are suspended in air. This is what I can see as the difference.
Why do you not just do a DWC? I have to agree with the others who say that the plants are overwatered a little.
Give it a chance... lets see how the yield turns out!