pH fluctuations in the feeding solution


Please forgive me in advanced…im still new to growing and still learning a lot.

With that said, I am doing a coco-coir based grow, where I have a reservoir mixed with my nutrients, and a couple air stones. Whenever I brew the solution, I tend to set the pH to 5.5 - 5.7. The problem I’m having is that the longer I let the solution sit, the higher the pH gets. I let it sit out for a few days (Was letting the coco dry up) and the pH jumped to 6.7. Any ideas why this would be happening? My plants don’t seem to have any deficiencies (Besides the salty fabric pots) thus far.

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Welcome to the forum.

Most growers will mix their nutrient solutions immediately before feeding. pH fluctuations in a standing solution will vary. I suggest only feeding freshly mixed nutrients.


Thanks for your quick reply MidwestGuy. Thank you for the welcome

I see. Are there ways to keep the pH fluctuations to a minimum without feeding the nutrients immediately before feeding? The problem im having is that the coco dries up twice a day, so I had to setup a standing solution connected to a digital timer since watering twice a day wasn’t feasible.

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Best to mix just before use. Otherwise you might as well be growing hydro for having to adjust PH in solution. You might look into using a wavemaker instead of air stones as it does a good job with less $$ on electricity. And it’s quiet.


Is this what you’re referring to?


Im interested too👍


Welcome to the community!! :clap:t2:

It’s basically the same thing that he’s talking about.

How much liquid do you have in your res?
What are you storing it in?

Nute brand? And how much?
Armore Si?
How do you test ph?
How do you test ppm’s or tds?

Might be best to fill out a support ticket to know more about your grow in order to give a more accurate answer.

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COPY/PASTE the below list into your forum post.

Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so; Or post
NA (non applicable)

-What strain, Seed bank, or bag seed (photo or auto)
-Age of plant
-Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF
-Vessels: Type and capacity of container (fabric, plastic, etc)
-PH and TDS of Water, Solution, runoff (if Applicable)
-PPM/TDS or EC of nutrient solution if applicable
-Method used to measure PH and TDS
-Indoor or Outdoor if indoor, size of grow space
-Light system List brand and wattage/spectrum
-Actual wattage draw of lights
-Current Light Schedule
-Temps; Day, Night
-Humidity; Day, Night
-Ventilation system; Yes, No, Size
-AC, Humidifier, De-humidifier,
-Co2; Yes, No

If growing Hydro some additional questions:

-DWC? RDWC? Autopots? Ebb and Flow? Other?
-Distance of liquid below net pot (DWC)
-Temperature of reservoir
-TDS of nutrient solution
-Amount of air to solution

Always try to upload a clear picture in white light of any issues you may have to allow the community to assist you.

Date Time Stage Grow # Strain Temperature (Daily Avg) Humidity
(Daily Avg)
New Solution? Liters of water added (Liters) Ph unadjusted EC unadjusted EC adjusted Ph adjusted EC of runoff Sensizym Coco Sensi B-52 Bud Ignitor Coco Big Bud CalMag
10/2/2021 11:57 AM Late Vegetative 2 Blue Dream 70 70.0% Y 22 2.0 6.3 2.3 40 80 40 0 0 0
10/3/2021 11:51 AM Late Vegetative 2 Blue Dream 70 70.0% N 8 7.0 2.0 1.4 6.0 2.1 16 0 0 0 0 0
10/4/2021 12:44 PM Late Vegetative 2 Blue Dream 70 70.0% N 7 7.0 1.5 1.8 5.8 2.1 0 20 10 0 0 0
10/5/2021 6:26 PM Late Vegetative 2 Blue Dream 70.2 71.6% Y 22 1.4 6.4 1.7 0 50 25 0 0 0
10/7/2021 2:58 PM Late Vegetative 2 Blue Dream 72.4 73.2% N 7 6.8 1.4 1.4 5.8 1.6 16 26 0 0 0 0
10/9/2021 9:47 AM Late Vegetative 2 Blue Dream 72.1 67.3% N 10 6.8 1.4 1.4 5.5 1.3 10 20 10 0 0 10
10/11/2021 2:03 PM Bloom week 1 2 Blue Dream 70.7 61.2% Y 22 1.5 5.6 1.1 0 40 0 20 0 20
10/13/2021 9:17 AM Bloom week 1 2 Blue Dream 71.2 62.2% N 7 6.8 1.5 1.1 5.4 1.1 20 0 0 0 0 0


I use to use canna nutrients with coco coir coz i didnt have worry about ph coz the nutrients would put the ph at the right level


Plants are looking great. :clap:t2::+1:t2:
How much water are you mixing in your reservoir? (22L?) every 3ish days? What are you using for a reservoir?

More than likely, your air stones are boiling off the PH balance, so to speak. It will drift back to its natural state.

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Thank you!

I used a 25 liter tote that I had laying around. For a new solution I fill it up to the 22 liter point then add my nutes.

Every other day I add another 7 liters to top off so I can adjust readings. So about 35-40 liters per week.

I replace the solution based on how it looks. Usually once a week.

And about the pH, that’s what I was thinking too. The water looks like it’s boiling with how much air I was pumping through the stones. I’ll reduce the air pump and see how that works

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I would think right now, you should be shooting for at least a 1.5 gal of water per day, per plant, especially during the transition. If you like to mess with the water aspect of growing have you ever thought about a hydro grow (rdwc)?

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You could make that grow a lot less expensive IMO. Keep’em growin! :+1:t2::v::sunglasses:

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1.5 gallons per day seems like a lot. They are barely retaining 1 gallon of water (Decent amount is runoff) so my digital timer is set to water 0.5 gallons to both plants in 12 hour increments. (35-40 liters = ~9 gallons = 1.5 gallons per day / 2 plants = 0.75 gallons per plant per day)

I’ve heard of Deep Water Culture (DWC) but never RDWC. I’m trying to find a system that is very hands off (A system where I can connect my nutrient bottles to a reservoir/digital timer would be excellent). I don’t have much free time each day to focus on the plants, so the less time I spend fidgeting with watering, the more effort I can put into inspecting and training the plants.

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Ok, let me say this, depending on how you water and how big your pot is, half gal twice a day is not that much less.
Most water once a day, it doesn’t matter how you water, just don’t let the coco dry out, especially if you have perlite mixed in with your coco.
I run an Recirculating Deep Water Culture (rdwc) and have had some plants that will drink almost 2 gal of water a day. Normally about 1.5 gal is pretty normal especially during the transition.
Your plants look great. I wouldn’t change what your doing if it’s working, and it is! :+1:t2:

My system is almost completely hands off. In hydro, more water = a more stable water condition when it comes to PH.

I run Jack’s nutrients. So, if I set my mix full strength and PH to 6.0 with 22 gal in my system, it will stay there till the cows come home. I don’t have to make adjustments till I feed the next time.

They actually have that. I would not know which one to buy. Problem with those systems are, you have to keep all of the probes clean. They will get dirty quick.
I guess if I had a huge system, it might be a good thing but with only two plants, for me it’s not worth it. :+1:t2::v::sunglasses:

From what I understand it is normal for the pH to drift slightly. I’m using a WaveMaker in my 5 gallon bucket reservoir. Made a fresh batch over 48 hours ago, pH was 6.52. pH is now 6.81. Only thing in the res is H2O and Jack’s 321. Just pH adjust the water again, then feed. I would only use the nutrients in the res for 4 or 5 days, then make a completely new batch.

This is the WaveMaker I would recommend over what @slinkcsubacca recommends. The one I bought has a magnet to hold it against a curved surface (like a 5 gallon bucket).

Welcome to the community, I have a 12 gallon reservoir and was experiencing PH drifting as well. I too had air stones but changed those out for wave makers and fill my reservoir with 4-6 gallons at a time. Temps in the reservoir will create issues as well, another issue I faced in the summer and started storing less in the res :love_you_gesture: