Ph dropping after 3 days

on friday i mixed my normal 5 gallons of nutrients so its ready for a monday feeding, i used molasses, & 1/2 of reccomended gh flora grow & flora bloom & cal mag & liquid kelp ,ph was 6.5 on friday & monday i tested again it was 4.5??? I usually feed within a few hours of mixing, so i never experienced this before?? thanks.

As the solution sits, gases exchange…O2, Co2…form water to air, vice versa. This alone will cause Ph drift. It your drift is excessive, it means thee is no buffer in the solution…your Kh may be off or there are nitrates/trites in the water. You are to expect some ph drift, it is a normal thing. If it is excessive, you need to either lower the amount of nutrients or add a buffer. In fish tanks, we used to add a bag of crushed coral. Even a small bag of charcoal will buffer it.
recommendations: mix less solution…add a buffer
things to examine - are nutes old?..Molasses LOWERS Ph…back off slightly
hope this helps

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good call mike, yes the nutes are old, i just drizzle the molasses & shake till the ph is around 6.5, i ususally feed within a few hours of mixing, so i dont normally re-check ph, but i will from now on… should i not use the 3 year old nutes? plants seem to be doing ok im at 12 weeks from germination using ff of soil & now 2 weeks into flower. glad your here mike. :+1:

Liquid nutes? 3 years is pretty old. They would have had to been stored properly. I do not buy the LARGE containers of nutes, they mostly go bad…cannot use them fast enough
FFOF - this soil has enough nutes to feed plants usually right into flower. Soil can be a living thing…rebuilding and repairing itself so it makes it hard to tell if the TDS are active, from soil or feedings. Salts are salts but NPK in a solution does grow weak…it degrades, if it is organic. That is the nature of organic.
If you do this long enough, you will learn to read your plants. They will tell you what they need. Learn to listen (we listen with our eyes, hands, noses)
Always check Ph before watering. Soil has an excellent capability of repairing itself and correcting ph imbalances. The ph may be low but the runoff is the true indicator. What comes out represents what is IN…not put in but IN the substrate. Ph has to be <3 or greater than 8 to really damage up front. We use 9 to kill mold and as a spray, the plants survive.


@mikes did you make sure to aerate the mix and make sure the liquid was in motion when checking the ph? Sometimes mixes might separate or when things react it will release hydrogen inside of the water and the exchanges of hydrogen can change ph.

If you aerate it and mix it it puts oxygen back in the water and will level the ph out more.

If aerating and remixing doesn’t help adding a slight buffer might help. Something like liquid kelp or even just some sodium bicarbonate to bring ph up closer to neutral.

Ph literally means potential hydrogen. Acids add hydrogen or h+ ions where as bases absorb h+ ions and create a buffering effect.

It’s why acids and bases react the way they do. Acids want to get rid of their hydrogen ions and bases want to take as many as they can.

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Good info, I mixed in 1 gallon jugs, & shaked & agitated it alot, but no other aeration, ill try to add some more kelp next time. I ended up diluting it with more 7.5 rain water, so they got a weak feeding this go around.