Aeration of feeding water

So for a couple of weeks now I have been mixing my coco nutes a week at a time, but was baffled as to why my PH in the water/nute solution would climb from 5.8 all the way to 8.1 at highest. After doing some research it was because I had a small airstone running in the nute mix to keep it mixed and add some oxygen to it. What happens is as you increase the oxygen level in water it displaces co2 out of the water, thus increasing PH. As an experiment I hooked up the same airstone to a co2 generator and popped it into another container with 5.8 water. Within 5 hours I had a PH of 4.2. So increasing the CO2 levels causes the oxygen to displace thus lowering the PH.
Just sharing this in case anyone else has experienced the same issue and was wondering what the cause was.

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excellent observation this is the reason when doing DWC you check ph several times daily.

Once I figured that out it made perfect sense why you get PH drift in DWC. I was getting it really bad, but I had two air pumps hooked to a 5" round airstone in my 5 gallon setup. LOTS of air going through it lol.

lol I have a pump rated for upto 16 plants running 2 my ph drift was crazy with only 1 when I started it

Actually, when aerating with plain air, you are more likely to see a pH drop, especially in plain water. Yes, extra CO2 tends to make things more acidic but less CO2 isn’t really the most important thing making it more alkali. I’ve never ever seen what you are describing as far as a rising pH with aeration under normal conditions, pretty much only dropping pH.

Normally plain air has enough CO2 in it that, again, the pH is more likely to drop than rise. But most nutrient systems are designed with alkali minerals to “buffer” pH and these will make the pH go up without enough CO2 or the normal biological activity that drives the pH down that these minerals are trying to counter.

Smaller reservoirs will always see more dramatic swings in pH. The plants themselves will make the biggest impact on pH because of their uptake at the roots, and a drive towards the acidic is especially noticeable during flower. This is normal and caused by ion, cation and anion exchange at the roots, and this is mostly related to the specific makeup of your nutrients and the needs of the plants at the time.

Too much aeration is not necessarily the problem, it is more so due to the size of the reservoir in relation to the size or number of plants, more reservoir means, both the aeration causes and the plant’s activity will make less of an impact on the reservoir’s pH.

Happy growing,



So in this case it is the fact that the nutes are buffered causing the PH to rise in the feed mix, and not necessarily the amount of air being pumped in? I am going to hook up the airstone to a plain container of un-nuted water and see what happens :smile: