Mixed nutrients water ph went up?

hi ,guys. need help.
i use soil for grow.
i had mix water bottle of the nutrients with ro water .
after done mix. ph is showing 6.3 , but next day i check with my ph meter in the bottle of nutrients is showing 7.0 ph .
i pretty sure my ph meter had no problem , but what is the reason why ph went up?
do i need to adjust ph every time?

thank u

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Co2 dissipating from the water will raise the ph. Nutrient solutions should be mixed and used, not stored

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pH definitely changes if a bucket of water sits out…may not be your meter my friend…

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Also bacteria has a tendency to raise pH (at least the benificials do when u brew them) I’d imagine any bacterial colony would.and even spring water bottles never used will grow bacteria after opening in less than a day. Prob not the case just thought it was a opportunity to educate a bit;)

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pH frequently changes, even with just water sitting out.
That’s why you always test before using it.

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If I mix a batch of feed I do it in a 1tr jug. I didn’t use it all one night as I had forgotten about it after going in for a bite and man did it smell fruity the following night. Mix it and use it right away, monitor your runoff and stay away from the chemical adjustments if possible. I had a nitrogen lockout and found it through my runoff PH. I just kept watering with no nutes till my PPM started to fall and my PH corrected itself :sunglasses:.
Edit: trust your equipment but keep it calibrated. Buy PH buffer solution for your PH pen, there’s plenty on here about it and good luck

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Mix and use within a few hours, otherwise the pH will change.

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Just curious,does it tend to drop or rise when letting it set?

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Don’t premix nutrients and let sit unless you don’t mind adjusting the ph again. If you want to store some than don’t worry about adjusting the ph until you’re ready to use it.

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In the absence of other factors (like bacteria for example) distilled water in an open bucket at room temperature will move down from 7 to a range of 5.5-6 pH as it reaches equilibrium with the air.

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