I don't have anything to add to the discussion but I have a question. Would it be feasible to dose urea exclusively as the nitrogen source?
I know this is a loaded question that pertains to ambient water column nitrogen concentration, among others. But assuming that I have chronic 0-5 ppm NO3 water column level (which I do...for shrimps and too lazy for test kits or whatnot), is it ok to rely on dosing urea for the plants at a rate of 1 ppm Urea (2.0649 ppm NO3 equivalent) every two days or whatever? My pH is in the low 6.
I figure, at worst, if no urea is consumed by the plants, then I will end up with no more than ~25 ppm NO3 over time, assuming 3x/week 1 ppm Urea dosages and 25% weekly water changes.
Will you offer some feedback?