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.

Thank you very much for that straight up answer. I'm beginning to wonder if you'd be farther ahead by either:

Using a single nute product, measuring PPM and topping off with that one nute as you go. Adjust pH only.

OR

Using a blended nute mix and ONLY adjusting pH. After you go through X gallons of added RO water, change out the whole deal and start with fresh, balanced nute mix.

Actually, since even a single nute product is a combo of several minerals and salts, the uptake of these components could be at different rates and therefore adding back even that single nute could cause a bad balance...

So really, while measuring the PPM as you go can maybe give you a little insight, it can't tell you what to do other than maybe change out the whole nute solution

You are perfectly correct on both counts. That is why I really feel the use of an EC meter is misunderstood.

One the issue of adjusting pH, that is also not too necessary. All of the standard nutes are pH buffered, and if you are topping off the rez with fresh water, the pH should stay stable until the nutrients (and their buffering agents) are slowly uptaken by the plant, then you have water out of the ratio of the buffering agents and the pH starts to rise. Time to change the rez and start fresh.

very glad to hear you say this. In your opinion is it even relevent to measure pH and salt levels?

yes and no. Definately less than others believe. Checking pH probably let's u get the most of your Nutes. U can wait to change your rez to when the buffer has been used up, or you can add pH down to continue with the same nutes after that. EC should give you an indication if your solution is too strong. If you keep the water topped off everyday and your EC is rising than your solution is too strong. If it falls everyday it is either too weak or just about right.

That's the whole game. Haven't been able to substantiate anything else.

Thanks very much

Good luck, I can tell you're gonna do well.