pH concerns

[Surfer Joe]

I noticed an odd thing today and was worried about having hurt the plant.
I mixed up fresh nutes to replace the bubble bucket and when I checked the pH it was high (7.8) so I brought it down to 5.7 with a few drops of pH down.
But when I did the same thing after having the air stones running in the fresh nutes, the pH was very resistant to change with the pH down, and I had to use a lot of it to get the pH down to 5.9.
In the process, I noticed that the pH stayed the same or even went up a bit as I kept adding more pH down and I ended up using a lot more than I would to lower the pH when the nutes were not being aerated with airstones.
Why does the air bubbling cause the pH to stay high or even go back up?
Should I pH the fresh nutes on their own before putting in the airstones and ignore if the pH goes back up?
Did adding a lot of pH down create problems if the aeration stops affecting the pH after a while?
I will check tomorrow to see if the pH has shot way down or gone back up, but I was wondering how experienced growers set their pH when adding fresh nutes?

 

[ROSTERMAN]

Let new nute water sit an hr or longer than do your PH reading before use
PH can change. Take reading with airstone off

 

[Surfer Joe]

Thanks, that’s what I normally do, but once I turn on the air stone, the pH starts going back up!
I hadn’t tested the pH like that before (with the air stone running) but wouldn’t it be bad for the plant to sit in pH 7.6 nutes for a day until I checked it again and tried to reset the pH?

 

[WeedHopper]

I always tested my PH in the DWC after adding nutes. Whatever the PH is in your DWC is what i would be testing. I never noticed the PH jumping up much once i added my mixed and phed solution to my DWC though.

 

[WeedHopper]

Found this for ya bro.

Why pH Levels Change in Hydroponics Systems
Several factors can cause pH levels to change in hydroponic systems. When the amount of the nutrient solution drops below one gallon, the solution becomes more concentrated as plants absorb the nutrients. This results in widely fluctuating pH levels. It is, therefore, important to monitor nutrient solution levels, keep the reservoir full, and regularly test the pH in the reservoir.

Both inorganic and organic matter can affect pH levels in hydroponics systems. For example, gravel and other inorganic growing media act as a buffer and cause pH levels to rise in media-based systems. In a natural environment, soil acts as a buffer in a similar way. To get an accurate pH reading in a media-based system, test the pH of the reservoir solution as well as the solution (leachate) that drains from the beds or bags that hold the plants.

Algae and bacteria are the main types of organic matter that affect pH levels. If pH levels rise in the morning and drop later in the day, algae may be the culprit. As algae consume acidic carbon dioxide during the day, pH levels rise and then fall by evening. On the other hand, bacteria from root disease can cause a dramatic drop in pH levels. As diseased roots decompose, bacteria will release acids into the hydroponic solution