it's not as much a matter of subtracting the 200 but it's what the 200 PPM is.

GH and Advanced have a micro made for hard water you may want to use. Or get a 5 stage RO filter and run it through that.
Zandor Reviewed by Zandor on . PPM ? about hard water My new spot has a ppm reading of 200 which we all know to be hard water...Can someone let me know if I really need a hard water nute solution(even for organic nutes) And if so which nutes are good for hartd water. Or can I subtract the 200ppm's from the final reading...or should I include the 200ppm's in the final measurment #? :confused: Rating: 5