PH keeps rising

Lathund · Mar 12, 2020

So I've made my first ebb and flow setup. Everything is working as it should, except for the PH!

This is in my veg area, I don't use any nutes in there yet, just tap water.
My PH meter is a cheap one but calibrated and stored in distilled water when not used.
The pump goes on every 3 hours for 8 minutes, enough to be at max level for a couple of minutes before it starts to drain.
The plants are in grodan cubes wich are set in 6" netpots with hydroton.

I have to use PH down almost every day. I add PH down until I am at 5.8-6.2. Next day it's up to 7.0-7.2.

I've been battling this for more than a few weeks now, what am I doing wrong?

Thanks in advance!

BuzzBob56 · Mar 12, 2020

Did you presoak and adjust your cubes, and wash your hydroton? Both of these can raise pH.

I wood · Mar 12, 2020

No nutes?
Homoepathic gardening, that is a new one to me.
Just water would have not much ability to buffer ph. Wild ph swings should be expected without any buffering ability.
What is sustaining the plant?
Seems like roots interacting in a solution of mostly water could easily affect the ph like you are seeing.
Add some nutrients of some sort and your ph issues will probably be lessened and your plants will have what they need to grow.

starke · Mar 12, 2020

Lathund said:
So I've made my first ebb and flow setup. Everything is working as it should, except for the PH!

This is in my veg area, I don't use any nutes in there yet, just tap water.
My PH meter is a cheap one but calibrated and stored in distilled water when not used.
The pump goes on every 3 hours for 8 minutes, enough to be at max level for a couple of minutes before it starts to drain.
The plants are in grodan cubes wich are set in 6" netpots with hydroton.

I have to use PH down almost every day. I add PH down until I am at 5.8-6.2. Next day it's up to 7.0-7.2.

I've been battling this for more than a few weeks now, what am I doing wrong?

Thanks in advance!

Ph probe storage guidelines:

"It is also important that you do not store the pH electrodes in distilled or deionised water as this has little to no ions present and will cause the ions to leach out of the glass bulb and will render your electrode useless."

In addition to the other suggestions which are all spot on, I would recommend checking the accuracy of your ph meter - or replace it.

Douglas.Curtis · Mar 12, 2020

The regular pH rise in a nutrient solution is driven by plants using the nutrients. When you add the standard 'cannabis' nutrients to water they act as a pH down. As the plants use the nutrients the pH will rise accordingly. The more gallons of nutrient solution you have the slower the pH rise will be. The smaller your volume of nutrient solution, the faster the pH rise will be.

The nutrient demands of a plant are mainly driven by the light intensity and environment temp/RH. Seedlings can use full strength nutes by day ten of life, as long as all other variables are correct.

Personally, I use r/o water for maximum stability and predictability with my pH, as well as maximum potential for clean cannabis.

Lathund · Mar 13, 2020

Thanks for all of the replies, I appreciate it!

BuzzBob56 said:
Did you presoak and adjust your cubes, and wash your hydroton? Both of these can raise pH.

Yes and yes.

The hydroton wasn't washed in PH controlled water though.

I wood said:
No nutes?
Homoepathic gardening, that is a new one to me.
Just water would have not much ability to buffer ph. Wild ph swings should be expected without any buffering ability.
What is sustaining the plant?
Seems like roots interacting in a solution of mostly water could easily affect the ph like you are seeing.
Add some nutrients of some sort and your ph issues will probably be lessened and your plants will have what they need to grow.

The reason for no nutes is that the grow space didn't work as intented, not yet anyway. We have cooler months and it went cooler than I expected. The plants are surviving and growing very slowly due to the climate. Basically I'm taking it extremely slow while waiting for the warmer months. I know, it's not good, but I don't have any alternate places to grow and I don't want to waste the seeds so here we are.

starke said:
Ph probe storage guidelines:

"It is also important that you do not store the pH electrodes in distilled or deionised water as this has little to no ions present and will cause the ions to leach out of the glass bulb and will render your electrode useless."

In addition to the other suggestions which are all spot on, I would recommend checking the accuracy of your ph meter - or replace it.

Hmm, this goes against what I've previously read and what the manual says. If not stored this way, how should they be stored?

Douglas.Curtis said:
The regular pH rise in a nutrient solution is driven by plants using the nutrients. When you add the standard 'cannabis' nutrients to water they act as a pH down. As the plants use the nutrients the pH will rise accordingly. The more gallons of nutrient solution you have the slower the pH rise will be. The smaller your volume of nutrient solution, the faster the pH rise will be.

The nutrient demands of a plant are mainly driven by the light intensity and environment temp/RH. Seedlings can use full strength nutes by day ten of life, as long as all other variables are correct.

Personally, I use r/o water for maximum stability and predictability with my pH, as well as maximum potential for clean cannabis.

Thank you for a very thorough explanation! I'll try adding some nuts and see where we land. I'd really like to install a R/O filter, but I can't. Not right now anyway.

Thanks again everyone, very helpful!

Esme · Mar 13, 2020

Never run rockwool without Nutes mate even if it's a little bit, I would PH Down to 5.5 and let it swing a bit but add nutes

Lathund · Mar 13, 2020

Esme said:
Never run rockwool without Nutes mate even if it's a little bit, I would PH Down to 5.5 and let it swing a bit but add nutes

Thanks for the advice! Anywhere I can read up on the theory behind it? Or if you don't mind explaining?

I've done a couple of grows a good while back, but back then I used hempy buckets, a lot more moving parts when it comes to hydro systems.

Frosty Nuggets · Mar 13, 2020

You can get special storage solution for ph pens.

SuperBadGrower · Mar 13, 2020

If you don't have storage solution, you can use the 4.0 PH test solution, it's almost as good

Newguy420 · Mar 13, 2020

PH the Res to ph5. 5 let it drift to
Ph6. 2 I used 200mm net pots with
Hydroton. I also flooded for 8mins
Make a syphon bell to get water to drain quicker. Cracking system also
Cover your table tray too

starke · Mar 13, 2020

Lathund said:
...
Hmm, this goes against what I've previously read and what the manual says. If not stored this way, how should they be stored?
...
Thanks again everyone, very helpful!

In Probe Storage Solution, 4.0 ph Calibration Solution or in a pinch plain old tap water.

ElGato · Mar 13, 2020

if you are running with just water there is no need to have a specific PH

Correct PH is for Nutrient uptake. No nutrients = no nutrient uptake by the plants = no need to PH the water

mj

Douglas.Curtis · Mar 13, 2020

starke said:
In Probe Storage Solution, 4.0 ph Calibration Solution or in a pinch plain old tap water.

Not sure what probes the new cheapie pens are using, but I've had a Jellas brand pH pen in r/o water for several years now. Calibration slips 0.1 every couple months, which is well within tolerances for a < $20 pH pen.

G.O. Joe · Mar 14, 2020

It used to be that manuals always said to use a storage solution - I used pH 7 buffer - but now some cheap pens say use water. They're both right.

Douglas.Curtis · Mar 14, 2020

I'll be they've made an absolute mint from storage solution sales. "Ooooh, and we have this special bottle of water for only $11."

Lathund · Mar 30, 2020

Hi guys!

Thanks for all the replies, and sorry for my lack of replies! Crazy times these days...

So I've tried adding nutes. And it's not really working as I'd expect, hear me out.

I'm using General Hydroponics MaxiBloom, the dry kind, powder if you will. Since it's my first hydro run I thought I'd start simple with the classic Lucas formula.

I dissolved the powder in hot water according to the lucas formula. EC meter has it at around 850ppm. PH around 5.8-6. So far so good!

I mixed up 40 grams of MaxiBloom and put it in my reservoir, ppm around 450 wich was what I was shooting for. I thought I'd start slow and ramp up as we go.

The problem: A few days later the entire reservoir is very "cloudy" and when stirring around in it there's a lot of white "flakes". And PH have spiked up to 8, highest I've had it.

Could cold water cause this? When I did my test it was in room temperature, but the grow area is still quite a bit colder. If it is due to cold water, is there another way to go? Except for the obvious wich would be to heat the water up.

Thanks in advance!

Douglas.Curtis · Mar 30, 2020

The first reason could be a reaction between the nutes and something in your tap water.

Here are a couple things you might look at as well. Try mixing with warm water instead of hot. When the temperature is high enough it will damage the solution. Keep the volume you're dissolving into large enough. Too concentrated of a solution will drop pH significantly until ilt's mixed into the nutrient solution. This low pH can also damage the solution, allowing elements to combine and precipitate out as flakes or silt.

Lathund · Mar 31, 2020

Douglas.Curtis said:
The first reason could be a reaction between the nutes and something in your tap water.

Here are a couple things you might look at as well. Try mixing with warm water instead of hot. When the temperature is high enough it will damage the solution. Keep the volume you're dissolving into large enough. Too concentrated of a solution will drop pH significantly until ilt's mixed into the nutrient solution. This low pH can also damage the solution, allowing elements to combine and precipitate out as flakes or silt.

Thank you for the speedy reply!

When reading your advice I can definitley see I might have gone too far with the hot water. When I did go with just warm water I felt that the nutrient didn't dissolve well enough, leaving a powdery residue on the bottom. Might not be a problem though and will possibly dissolve over a longer period of time?

The hydro reservoir holds around 70L of water. I mixed 20g of nutrients in to around 1-1.5L of water before I poured it in to the reservoir. Is this a large enough solution?

And to be extremely clear, I need to purge the entire reservoir before starting over I guess?

Thanks again!

superpedro · Mar 31, 2020

Hi.

What acid do you use?

If you use little or no nutrients, nitrogen based pH-down may effect your NO3-NH4 relationship. That will again effect your pH.
In your case i suspect to little NH4 in your solution compared to NO3.

Found this information on the topic.

Read this: https://www.cannagardening.com/how_ammonium_nitrate_ratio_affects_your_plants

Note: If you grow cold, pay attention to this:
"At lower temperatures, ammonium nutrition may be a more appropriate choice, because oxygen and sugars are more available at root level. Additionally, since the transport of nitrate to the leaves is restricted at low temperatures, fertilization based on nitrates will only delay the growth of the plant. The effect of the substrate temperature also depends on plant species."

And:
The effect of ammonium and nitrate uptake is especially important in soil-less media, where the roots can affect the pH of the medium more quickly because their volume is relatively large compared with the volume of the medium. To prevent the pH of the medium from changing too rapidly, an appropriate ammonium/nitrate ratio and substrate temperature are essential, according to the plants growth stage.

PH keeps rising

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