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pH dropping with Hydro Grow soft


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#1 camerasforears

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Posted 07 March 2012 - 02:12 PM

Hi,

Switched into 12 three days ago and topped them up with the last batch of Hydro grow soft on the same day. I noticed today though that on my bigger plants the pH has dropped down to almost 4.8 when it was started at 5.8. EC has remained risen slightly from 1.66 to 1.9 on the ones that are drinking the most.

The smaller ones are showing no sign of pH movement. I was wondering if this was due to the nutrient requirements changing due to shifting into flower but I thought it would be happening across the board and not just to the big plants.

Normally the pH is pretty rock solid with these nutes and I am very happy so far!

About my setup

Using RO water (probably don't need to I know as my water is pretty soft already) around 80W per sq ft light with very good circulation. Tops of the plants are around 23 or 24 degrees and below is around 18.

I do a complete water change every week rather than just topping up. Using DWC, big ones are drinking almost 4 litres a day. But smaller is less, around 2 litres ish.

Nutes are all mixed up in one big tank so I know that they are all the same strength.

If anyone has any advice for me that would be great, I hope this is just a momentary blip from switching to 12 but if pH continues to drop I will have to look at different solutions.

TLDR - There is a correlation between the amount a plant drinks and the pH bottoming out - can this be solved and is there a particular nute it is removing quicker to cause this drop? Should I bump up the EC to 2.0 so there is more of the thing it is removing and hopefully will be better buffered?

#2 cf

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Posted 07 March 2012 - 05:42 PM

If you have soft water forget the ro machine, getting nutes ph stable with no buffer is a faff, I had hard water but using an ro machine meant adding back either some tap or calmag.
Since you have soft water why dont you just use that and let it buffer your solution ?

BTW after several years making ro water I changed to a hw nute and couldnt tell the difference.
I'm on my second run with PM hard water nutes in nft at the moment and liking them a lot :hi:
“There is no reason to accept the doctrines crafted to sustain power and privilege, or to believe that we are constrained by mysterious and unknown social laws. These are simply decisions made within institutions that are subject to human will and that must face the test of legitimacy. And if they do not meet the test, they can be replaced by other institutions that are more free and more just, as has happened often in the past.”

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#3 camerasforears

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Posted 07 March 2012 - 09:26 PM

If you have soft water forget the ro machine, getting nutes ph stable with no buffer is a faff, I had hard water but using an ro machine meant adding back either some tap or calmag.
Since you have soft water why dont you just use that and let it buffer your solution ?

BTW after several years making ro water I changed to a hw nute and couldnt tell the difference.
I'm on my second run with PM hard water nutes in nft at the moment and liking them a lot :hi:


My pH has been pretty rock solid up till switching to 12. But I think your right, maybe I will mix back half and half RO and tap.

Once I mix up the ferts I am using silicon to bring the pH up, around 0.1ml to L to bring it up from 4.7 to 5.9 Wonder if I would be better just using K OH instead..

Surely when you add the nutes to the water that provides a buffer in itself. Does calcium and magnesium have that much effect on holding pH?

I haven't had a problem with using the RO water and not seen any deficiencies for last attempts but I have just changed to plant magic from another brand. My pH used to be all over the place but I have been pretty impressed with how PMP was keeping steady until now..

I left them for more than 10 days during veg and when I came back pH had only shifted 0.2!

Thanks for your input

Edited by camerasforears, 07 March 2012 - 09:28 PM.


#4 cf

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Posted 07 March 2012 - 09:42 PM

I used lucas ( GH 2 part formula) coz it was the most prodigiously documented regime on Overgrow and Cannabis World, and there was a dearth of info on uk RO use.

I found GH nutes difficult to stabilise until I used epsom salts and cannas calcium (my own cal mag!) . GH were bang on Ph striaght out of the bottle but wondered about as bit after a day or two. Once the mg and Ca was in the tank I could use a little acid and suddently no problem. All i assumed was that the sulphates and carbonates and whatnot in the mg and ca gave the solution a good 'base' to kick against ...(I'm using base not in a chemistry lesson sort of way)
Using a small % of tap did the same. I would also like to knwo why the nutes dont have this buffer effect but I imagine I'd be out of my depth quite quick with the answer :stoned:
“There is no reason to accept the doctrines crafted to sustain power and privilege, or to believe that we are constrained by mysterious and unknown social laws. These are simply decisions made within institutions that are subject to human will and that must face the test of legitimacy. And if they do not meet the test, they can be replaced by other institutions that are more free and more just, as has happened often in the past.”

Noam Chomsky

#5 camerasforears

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Posted 07 March 2012 - 09:55 PM

I think you hit the nail on the head.

I did some research and the main buffer agents ARE the Cal and Mag - hence why in limestone rich areas the water is that much more buffered or for another word - hard. I would imagine this is pretty much the sole difference to the Hard and Soft water nutes. There must be a wee bit CalMag added in the Soft to bring Calcium and Magnesium up to 200 ppm ish from a base of less than that.

The hard nutrients probably have no Calcium and Magnesium in it so the levels don't get so high that there is lockout.

I had incorrectly presumed that most the buffering agents could have come from the NPK but that is not the case..

I had thought about Lucas formula for this batch but went with the PMP range as everyone was raging about it, been pretty effective so far but I think with your advice I could take it that bit further and target the pH shifts as well.

Thanks again!

#6 camerasforears

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Posted 16 March 2012 - 04:25 AM

Just to follow this up.

Added a wee bit of tap water to my nutes (approx 20% with a 0.15 EC) and it seemed to balance my (albeit moderate) fluctuations nicely..

I would advise anyone else going RO to follow this route. I wasn't getting any deficiencies I could notice but it certainly made life a bit easier.

I ordered some CalMag though for next time.

#7 dastardlyandmutley

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Posted 17 May 2012 - 02:43 PM

Ha! camerasforears, it seems I am following you around nin the forums these days!

So what brand calmag did you go for as I understand u r in the uk.

and is the ratio pretty much like for humans- two parts calcium to one part magnesium?

i am still wondering whether the Lucas formula can be used if you add 20-30% tap water and therefore add about 0 .2 EC in my case or whether to add calmag to the get about te dame 0.2EC
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