Anyone reading this thread to learn about low maintainance/water quality issues should note that this tank has ZERO nitrates after months of no WCs. I strongly believe that it is due to the soil base. The plants may well have been able to achieve this without the soil but my experience (quite limited) is that they don't tend to get it all all the time without soil. The anaerobic soil allows them to easily convert the nitrate back (with the help of some anaerobes) to a nitrogen form they can easily consume.
If there has been an issue (and I think there has) it is dissolved organic solids. In the future I will do water changes or, if I wanted to avoid the WCs, experiment with seachem's Purigen, which claims to deal with this issue.
I will stick with the soil base because it is a simple and effective, automatic, low maintenance, denitrification system. I am glad I tried this before one of those complex denitrifiers you read about people fussing with forever. This is a way better way to go.
This was an experiment and my tank won't stay like this. I quite enjoy some elements and will retain them while advancing the aesthetic value of the tank in the future. It is, likely to retire from the experimental arena and become a display tank.