If I am reading the response from High Brix Manufacturing Inc correctly they dont think you can have the right environment in hydro to raise the brix. They sell soil and additives for soil, so I think they may be biased. But I will let you know how the conversation goes.

No it does work the same way without soil for a medium. Even though we discuss chemistry, the biology contribute  to the success of the system. Soil is need for the environment of the biology to contribute to the efficiency of the system.