New Grower Advanced Nutrients pH Perfect 3-part GMB - Need Advice

[Muddy]

So if I need to add more cal-mag to correct a deficiency would I initially just add enough to get starting ppm in that 100-125 range then add base nutes then add additional cal-mag after?

Yes, add cal/mag to that level, then add your base nutes, then any supplements. At that level you shouldn't see any cal/mag deficiencies but if you do, then just add a little more.

 

[Hansbricks]

Yeah I use LEDs so seem to need more cal/mag. I'll try making sure my starting ppm is in that range tho and see if that makes a difference. Thanks for the help bud

 

[Dr Who]

conductivity and pH

Hans - what's the pH of your water before and after you add the nutrients to it? You mention that your conductivity reading is high, but also that your pH is low (perhaps below 6.0).

Soft waters tend to have low pH, low hardness, and consequently low TDS/conductivity
Hard waters tend to have high pH, high hardness (lots of Ca), and a high conductivity

But... and I apologise in case this causes any confusion, the relationship between conductivity and the concentration of dissolved salts (i.e. TDS) starts to fall apart at low pH (perhaps somewhere below pH 6 ish). Basically the "acidity" is a much more effective conductor than the salt, so a low pH water will give an apparently erroneously high conductivity reading. The conductivity is indeed high, but the concentration of dissolved salts is not nearly as high as you would expect from the normal conductivity-TDS relationship.

I would suggest you check that this issue isn't complicating things for you.

 

[Hansbricks]

Hans - what's the pH of your water before and after you add the nutrients to it? You mention that your conductivity reading is high, but also that your pH is low (perhaps below 6.0)

Hey Dr. As I stated initially my tap water has the high TDS (370ppm - pH ~7.4) I don't have a conductivity meter. I haven't used tap water for my nutrients tho due to this high TDS, I've been using only RODI water, if I don't adjust my feed the pH is like ~5.5 which is too low. I'm not really sure what the starting pH of my RO water is... my understanding is that RO water should be around 7.0 but when I measure it I get a much lower reading (I've also read that you can't accurately measure RO water tho due to the lack of ions in the water)

I'm going to try what Muddy suggested and make sure my starting ppm is in the 100-125ppm range, if that doesn't work I might try mixing in tap water with my RO maybe like 2/3 RO, 1/3 tap water. I will report my finding.

 

[Dr Who]

Hans, at least you know that your RO water is good, pH 5.65 is the theoretical pH of ultrapure water at equilibrium with the atmosphere. I am surprised that you would need to add base if the nutrients are buffered though, because the water should have virtually no existing buffering capacity.