Quote Originally Posted by Projman
When measuring nutes (PPM, CM, etc) and you're using 2-3 nutes, how do you know what to add in / top off?

I realize some don't touch the nute load at all until after a few gallons of RO have been added in, then flushed, then new nute mix. I imagine these people never measure nute loads.

Others measure the nute load constantly, just like measuring pH.

Not sure which is the best way to go.
The answer is you cannot. You are asking the most intellegent question of Nute mixing. People who top off mistakenly believe that plants drink the nutes uniformally, and they top off the rez uniformally. That creates toxic build up of certain Nutes and deficiencies of others.