No i calibrated my meter its a blue lab ppm pen. It reads my tap water at 900 ppm.
I see these charts that show certan plants for early veg at 350 ppm. but how do I achieve that if my ppm on my tap water is reading at 900 ppm?
so my ppm reading is 900 can I still grow in a DWC set up.now I am new to this whole ppm thing. so if my ppm of my tap water read 900 then it do I add that to my ppm readings? for example do I need to add in the PPM or minus the PPM to get to my target number ?
Example: if i want a ppm of 300...