26.2mg/l estimated average from water report in the tap. Cut that to a quarter for mixing with three quarters RO, so 6.55mg/l NO3 in the water change water.
Dosing APF’s standard EI measures throughout the week should keep NO3 above 20ppm from the second day. First day I dose micros after water change to take advantage of the very low phosphate levels to aid iron uptake and good estimated calcium to iron ratio. Negates the need for more stable chelated iron sources. If it’s a serious trim seaweed extract for the hormones at water change as well.
TDS starts at the 200-250 at water change and 300-350 on the seventh day before next water change.
If water change is straight tap TDS is always above 400-450 at start of the week.