Can't keep pH under 6.4

[rrog]

I have a very accurate Milwaukee probe with all the calibration solutions.

Have always needed to add pH down about daily. Same is happening now. Nutes at 1/2 strength, started with RO water and CalMag+

I check pH daily and it's always high. This is a daily thing. Buffering seems to be occurring closer to 7 than 6.

I'm pretty methodical which is why this is perplexing.

Thanks for any thoughts.

 

[RedXIII]

What kind of setup do you have? What medium are you using? I use hydroton and have noticed that you need to presoak it for a while in a properly pH'd solution (readjusting pH as needed until it stays where you want it). I did not do this at first and noticed my nutrient solution suffering a daily rise in pH for a while until the hydroton buffered out at the pH I kept adjust my res to. Hope this helps!

 

[HeadyPete]

If you use rockwool it will buffer the ph up as it is spun from basalt rock, which contains calcium and magnesium.

It needs to be conditioned first. Plenty of info around here for you to search.

 

[FreezerBoy]

What's the EC doing?

 

[little-soldier]

check for root rot as it seems to brings the ph up. If its not the case and you are using rockwool follow headypetes advice.

 

[rrog]

I believe it could be the Hydroton. I conditioned the small Growdan, but not the Hydroton, though I rinsed it thoroughly, but not pH balanced.

I'll just have to keep adjusting pH until it balances

I'm doing a constant drip with DNF nutes

Thanks so so much for the great ideas. Very cool of all of you.

 

[rrog]

The biggest contributor may be the CA+ on the CalMag+, buffering my pH up. I have to re-think the CalMag

 

[stinkyattic]

The Ca+ isn't going to buffer up your pH significantly- in lime, it's not the Calcium that's the buffer, it is the Carbonate ion.

Hydroton raises pH if not pre-rinsed. You have to soak it at 6.0 for as long as it takes to set the pH- check a couple times a day and keep adding acid until it stabilizes. IF not pre-rinsed, it WILL raise your res to over 7.0. In my experience, dropping the res pH of a running system 2x/day, it takes about a week to stabilize untreated hydroton. Yes, I have also made this mistake!!!

CalMag is designed to be used in any type of system and if you have RO water you have no choice but to use it- just run it, but pre soak your media!

Give information on res volume, how much RW and HT is used in the system, and what brand and type of nutes you are running.

 

[rrog]

I received this observation on another forum:

QUOTE:
You are buffering with the calmag+
and you should be using Potassium silicate,
potassium hydroxide & potassium carbonate.

The calcium will take a long time to stablize,
and by then it is time for a change out,
because you have added so much acid.

Stop using the CM+ and get some Barricade or Silica Blast,
and some GH powdered pH up.

Your pH will stablize if you use the barricade first
and then the carbonate and hydroxide to finish the buffer.

So I'm a little lost

 

[stinkyattic]

What you posted above from the other source completely ignores the fact that all buffering aside, your plants REQUIRE calcium for healthy growth, and none of the products listed provide that. Plus the fact that you complain of RISING pH and the poster states that you should be using KOH/ pH UP. The WHAAAA?! Not gonna help you one bit! That's going to make it WORSE!
Silica Blast is a Si supplement. It's not meant to be used as a buffer; it's to strengthen cell walls against arid conditions and mite attack, among other things.
IMVHO that is not good advice that you were given. I do this [water chemist] for a living.
Your problem is improperly prepared hydroton. Jsut suck it up as learning, and keep dropping the pH with a correct pH down (Phosphoric acid) until it stabilizes on its own, then do a complete res changeout to get rid of all the salts from the neutralization process. You won't see this problem again.

 

[rrog]

Thanks a lot Ms. Attic. I'll do as you say and keep adding acid. Crazy stuff. Side note The DNF can some CA in it, I believe. I'll double check.

I'll also check that my pH down is Phosphoric Acid.

You've been really helpful and generous with your time and talent, I must say. Thanks again

 

[rrog]

El Gato, Thank you as well.

I just realized that the reason this pH rising issue is worse now is because I went from scheduled 15 minute drips to a constant drip. Much more interaction with the Hydroton...

Also, my pH down is Nitric Acid, I believe, from Technoflora. Should I trash the stuff and get Phosphoric?

 

[dankaholic]

yup, same thing happend to me even after i rinsed the eccess residue from my hydroton. it took a week, more like 5 days to start to stabilize. been cool since, i love it. just keep at the acid, unless you can use something more friendly. nitric acid i think is a by product of the phosphorus ph down. i think thats a bad thing. my plants lived thru it. good luck

 

[Ganoderma]

Have you tried to PH adjusting your water before you add in your nutes? I have found that when i've had this same problem that doing this solves the problems.

 

[stinkyattic]

Nitric acid isn't a byproduct of pH down.
It DOES work as pH down; however, it is a monoprotic acid and you will use more than if you are running Phosphoric acid, H3PO4, whcih donates THREE hydronium ions instead of the one from Nitric. It is also safer to use in flower, as Nitric acid puts excess N in your res, and this inhibits budset while encouraging excess foliage.

Any pH adjustment you make to your res should be after adding the nutrient solution, to take into account any contributions that the fertilizer components themselves have to the pH. pH is a WHOLE PICTURE kinda deal; everything you add to your res that is ionic can and will change it to some extent.

 

[rrog]

I adjust pH after everything is added and mixed well for an hour or so. That seems to be the best plan.

I'll toss this cheap pH down from Technoflora and get some Phosphoric Acid. Not sure what the brand name might be for that. AN, maybe? I'll look around.

Also, I think I'll be adding Hydroguard to the mix. I've heard great things about the combo of Hydroguard and Hygrozyme. I'll permanently omit the Peroxide, obviously.

 

[rrog]

General Hydroponics has a Phosphoric Acid. I'll try that

 

[TanzanianMagic]

I have a very accurate Milwaukee probe with all the calibration solutions.

Have always needed to add pH down about daily. Same is happening now. Nutes at 1/2 strength, started with RO water and CalMag+

I check pH daily and it's always high. This is a daily thing. Buffering seems to be occurring closer to 7 than 6.

I'm pretty methodical which is why this is perplexing.

Thanks for any thoughts.

You could put the hydrotons in a tub, and ph the water to 5.0. That way, the carbonate ions in the hydroton will be saturated (if that's the word) much quicker.

The buffering capacity is limited, but it just needs enough acid (or time) to soak it all up, so to speak.

I've had a similar problem with high ph tapwater a while back. It just needs time and acid to be remedied. Good luck with your grow.

 

[rrog]

That's exactly what I should have done Tanz. The Hydroton should be about done with this nonsense I'm hoping.

 

[rrog]

Just an update. I've harvested my three plants. pH never did get under control. I still blame the hydroton I was using. Moving to an actual bag of Hydroton brand. Doing some testing and see if this works better for me.

The other Hydroton came in boxes, obviously from some larger bulk packaging. May have been some lower quality Hydroton knock off.