That's a really interesting idea, the only problem I can see is that you might have ammonia spikes as the dirt brakes down in the substrate. I think that would be avoided by using MTS. If you don't have any fish in the tank I would give it a go just to see if your hypothesis could work and then measure the results. But if your not interested in running an experiment you could just go with root tabs.
But I bet someone with more knowledge then I has done this or something similar and can give you a clearer answer.
But I bet someone with more knowledge then I has done this or something similar and can give you a clearer answer.