Rather than apporaching this from a microbiologist view point, try a Botanist :gw

What do plant assimilate besides NO3?
NH4.

What happens when NH4 is added via the bacteria pathways? NH4=> NO2=> NO3.

What happens when the plants get a hold of NH4? => Glutamine, fixed nitrogen, no longer part of the water column.

No NH4, no NO2, no NO3.

So crank the heck out of the plant's needs, lights/CO2 etc, make sure you have K+, PO4, Traces.

Plants can use 1.0 ppm per day or close to it of NH4.


Do a larger water changes, say 80% etc, then crank the plants. Need more removal? Buy some cheapy plants.

Regards,
Tom Barr