Great thread! Much appreciated for the deep analysis of some of you!
From my experience I would be inclined to say bacteria *can* outcompete plants at N uptake. Bacteria works without light as well. Whatever Ammonium gets in the water it will be taken by plants during the photoperiod, then comes the night. Bacteria will strip whatever Ammonium is in the water and plants will need to consume energy for Nitrate processing.
Unless a soft spot is hit with the bio load there will be problems in the long run. Currently I'm facing a constant water acidifying effect because I have an Eheim 2080 hooked to a 300L tank. Which is 4 times smaller than the tank size for which this canister was designed.
Bacteria generates H+ as a byproduct of Ammonium and Nitrite oxidation. I will soon start a new tank to test this method. Will use just a powerhead for water circulation, some lava rock bits, zeolite, potting dirt and inert gravel. I have some AquaMedic Volcanit leftovers.