Balancing out Nitrates and Potassium

[Stephen Eugene Robinson]

I primarily want to grow tomatos and squash.  I believe I have a deficiency in Potassium, and I have been dosing with 5-10 grams of no-salt most days (KCl).  Truth is, I am dosing blind.  I don't know how to calculate the dosage of KCl I need to balance the Nitrate I have in the tank which I measure at about 200 ppm. 

 

I make the assumption that if Potassium is the limiting element, then my nitrate level will be drawn out with the proper dose of Potassium.  Can anyone verify this?