Andrzej Konarski wrote:
I stay at about 25 ppm adding 40 ppm per week and changing 1/6 of the
water.

And what do you want ot change ?
I cannot understand You !!!
You have high no3 and do You want to add nitrates or amonium ???

I have to add Ca or Mg to keep NO3 crashing to 0...
My tank consumes 40 ppm NO3 per week that I have to add...
Unfortunately Ca and Mg are added in the same time !

Philippe