Do not rely on your test kit to give you accurate results. Adding 1/4 tsp of KNO3 to 20 gallons of water will put the nitrates right around 10 ppm. Which is right where you want to be.
And yes, pick up some KH2PO4 and a trace mix like Plantex CSM+B.
See here http://rota.la
So you're sayin I should stick with 1/4 tsp instead of upping to a 1/2 tsp? It would coincide with what Django said about keeping low dosages I suppose. And why KH2PO4? How does it benefit the plants?
Does anyone have a link that would explain how plants utilize each fert? Or rather, the effect of the ferts on the plants directly?