I don't want to limit potassium. I was just concerned that since I was not dosing KNO3 because I believe NO3 to be high enough, that I was in essence limiting potassium which I did not want to do. I thought maybe I could offset by using a higher dose of KH2PO4. How far off can the hobbyist test kits be? I am using the API one, and coroborating with strips (which I know are inaccurate).

Basically I have young angelfish, and some Diamond tetras in the tank that I bred and I want to encourage to grow and do not want the nitrates to get too high.