RDWC PH typically goes up or down ???

[Tasman69]

Hi Team , just wondering if theres a normal trend in RWDC , where ph typically creeps up or down in veg and or in flower . In my dwc I usually add ph down if anything , in veg and ocassionally ph up in flower . This is my 1st grow in RWDC and I am using a dosing pump for nute and ph . Obviously theres no point setting it up for down if its likely to be dropping . I know its simple to swap from up to down but i work away for weeks at a time and are mostly fully automated . Any observations would be appreciated . I run at about 1100ppm , 1.8ec , give or take . Water temp around 21c. Thanks From New Zealand.

 

[Delps8]

Typically, as nutes are taken up, pH will tend to rise. Emphasis on "typically" and "tend to".

For my last grow and for the last few weeks of the previous grow, pH would drop for a few days after every res change and then gradually start to rise, perhaps 0.1 units every few days. The last grow was Gorilla Glue, the grow before was Gelato, and both were autos.

What changed? I switched from Botanicare Kind to Jack's 3-2-1 (mixed 3.79-2.52-0 because there's a lot of Mn and S in the two nutes).

As a new grower, I followed the "Wonder Chart" document religiously and chased pH all the way down to EC 0.6. No bueno on that. These charts have been floating around for years; I've given them new names. They offer good general guidance and, being completely new at this (I just finished grow 4 - one in 2017 and three since 1/21), I "followed the directions" and ended up with my dick in my ear, speaking metaphorically, of course.

The pH drop could have been from not adding the Epsom salts - I don't understand nutes at the ion exchange - but, as a grower on another site explained to me, the drop in pH is simply a result of how the plant was taking up nutes and there was nothing to worry about. He certainly was right. Both grows did well, the last one yielding 729 gm from two autos in a 2' x 4'.

Like you, I considered getting a doser but I decided against it. One reason for that decision is that I think it's good to develop an understanding of what's going on in the grow environment rather than "paving over" issues with more chemicals. Having been through those grows, I'm glad that I didn't because it was a reproducible behavior and my preference is to change my nute mix to get a res that's 100% stable without intervention.*

Hope that makes sense.

*Writng this posting reminded me that Bugbee did a paper on managing nute solutions in recirculating systems and he listed the chemicals that are taken up very quickly.

I'm thinking one of those is what's dropping my pH.

 

[Tasman69]

Typically, as nutes are taken up, pH will tend to rise. Emphasis on "typically" and "tend to".

For my last grow and for the last few weeks of the previous grow, pH would drop for a few days after every res change and then gradually start to rise, perhaps 0.1 units every few days. The last grow was Gorilla Glue, the grow before was Gelato, and both were autos.

What changed? I switched from Botanicare Kind to Jack's 3-2-1 (mixed 3.79-2.52-0 because there's a lot of Mn and S in the two nutes).

As a new grower, I followed the "Wonder Chart" document religiously and chased pH all the way down to EC 0.6. No bueno on that. These charts have been floating around for years; I've given them new names. They offer good general guidance and, being completely new at this (I just finished grow 4 - one in 2017 and three since 1/21), I "followed the directions" and ended up with my dick in my ear, speaking metaphorically, of course.

The pH drop could have been from not adding the Epsom salts - I don't understand nutes at the ion exchange - but, as a grower on another site explained to me, the drop in pH is simply a result of how the plant was taking up nutes and there was nothing to worry about. He certainly was right. Both grows did well, the last one yielding 729 gm from two autos in a 2' x 4'.

Like you, I considered getting a doser but I decided against it. One reason for that decision is that I think it's good to develop an understanding of what's going on in the grow environment rather than "paving over" issues with more chemicals. Having been through those grows, I'm glad that I didn't because it was a reproducible behavior and my preference is to change my nute mix to get a res that's 100% stable without intervention.*

Hope that makes sense.

*Writng this posting reminded me that Bugbee did a paper on managing nute solutions in recirculating systems and he listed the chemicals that are taken up very quickly.

View attachment 5186972View attachment 5186973 I'm thinking one of those is what's dropping my pH.

Cheers for that and the chart. I have had no real drama with my dwc so hopefully the RDWC will play the game . I will press on with the nute pump and the ph pump , got them now so kinda keen to play with my new toys . A friend is having better results ( he works away alot also ) , using the dosing pumps . I fully agree about not introducing extra chemicals where avoidable but not often having someone to do the normal checks makes this technology a potential game changer (fingers xd) !!! Anyway , thanks delps , you have given me a fair bit to consider .

 

[rkymtnman]

and the ph pump

i agree with delps. if only 1 ph doser, definitely for ph down. if you need to start using alot of ph up, you probably don't want to be away from the rdwc for too long so you can check for problems IMO.

 

[smokey0418]

In my set up , if I had my nutrition at 1.8 ec my ph would rise .

What also would rise is the ec.

Personally i try to get is were the ph is quite stable (moves .1) in 12-24hrs and the ec stays the same and or drops 10-50 ppm and I can monitor the drop, or rise.

sativa at this time, ec 1.18

Good luck with the grow.

 

[Billy the Mountain]

pH generally rises as Nitrogen is used in hydro mediums

Most hydro nutes are ~90%+ Nitrate (NO3-) and just a small % of Ammoniacal Nitrogen (NH4+)

If roots uptake nitrates, they release bicarbonates - pH rises

If roots uptake ammoniacal nitrogen, they release a proton - pH drops

 

[Tasman69]

In my set up , if I had my nutrition at 1.8 ec my ph would rise .

What also would rise is the ec.

Personally i try to get is were the ph is quite stable (moves .1) in 12-24hrs and the ec stays the same and or drops 10-50 ppm and I can monitor the drop, or rise.

sativa at this time, ec 1.18

Good luck with the grow.

cheers smokey , trying some "mimosa shot" and "hypnotic". Will probably ease the ec back to around 1.2 . Cheers for the info

 

[Tasman69]

pH generally rises as Nitrogen is used in hydro mediums

Most hydro nutes are ~90%+ Nitrate (NO3-) and just a small % of Ammoniacal Nitrogen (NH4+)

If roots uptake nitrates, they release bicarbonates - pH rises

If roots uptake ammoniacal nitrogen, they release a proton - pH drops

Thanks Billy , thats what I generally observe too. Im going with ph down . All going well it wont use to much .

 

[Delps8]

pH generally rises as Nitrogen is used in hydro mediums

Most hydro nutes are ~90%+ Nitrate (NO3-) and just a small % of Ammoniacal Nitrogen (NH4+)

If roots uptake nitrates, they release bicarbonates - pH rises

If roots uptake ammoniacal nitrogen, they release a proton - pH drops

Time to break out the Ouija board - Jack's 3-2-1 doesn't have any ammoniacal nitrogen or any urea yet I still get three days of dropping pH.

 

[rkymtnman]

Time to break out the Ouija board - Jack's 3-2-1 doesn't have any ammoniacal nitrogen or any urea yet I still get three days of dropping pH.

do you run an airpump/stones?

 

[Delps8]

do you run an airpump/stones?

Good question. Yes, both.

Air being pumped through water can change pH so I ran a test in 10/21. I ran the air pump for a couple of days with nutes in the res and saw no change in pH. Perhaps that's due to the buffers in the Jacks?

 

[LKABudMan]

pH will go up when the plants are consuming more Anions and go down when they're consuming more Cations. Mine always seem to drift up in Veg and down in Flower. I just had to pull out my pH up for the first time in week# 6 of flower, they crashed all the way down to 5.4 twice!

 

[Sorting1]

Typically, as nutes are taken up, pH will tend to rise. Emphasis on "typically" and "tend to".

For my last grow and for the last few weeks of the previous grow, pH would drop for a few days after every res change and then gradually start to rise, perhaps 0.1 units every few days. The last grow was Gorilla Glue, the grow before was Gelato, and both were autos.

What changed? I switched from Botanicare Kind to Jack's 3-2-1 (mixed 3.79-2.52-0 because there's a lot of Mn and S in the two nutes).

As a new grower, I followed the "Wonder Chart" document religiously and chased pH all the way down to EC 0.6. No bueno on that. These charts have been floating around for years; I've given them new names. They offer good general guidance and, being completely new at this (I just finished grow 4 - one in 2017 and three since 1/21), I "followed the directions" and ended up with my dick in my ear, speaking metaphorically, of course.

The pH drop could have been from not adding the Epsom salts - I don't understand nutes at the ion exchange - but, as a grower on another site explained to me, the drop in pH is simply a result of how the plant was taking up nutes and there was nothing to worry about. He certainly was right. Both grows did well, the last one yielding 729 gm from two autos in a 2' x 4'.

Like you, I considered getting a doser but I decided against it. One reason for that decision is that I think it's good to develop an understanding of what's going on in the grow environment rather than "paving over" issues with more chemicals. Having been through those grows, I'm glad that I didn't because it was a reproducible behavior and my preference is to change my nute mix to get a res that's 100% stable without intervention.*

Hope that makes sense.

*Writng this posting reminded me that Bugbee did a paper on managing nute solutions in recirculating systems and he listed the chemicals that are taken up very quickly.

View attachment 5186972View attachment 5186973 I'm thinking one of those is what's dropping my pH.

I had an issue with my DWC Setup were the PH was turning acidic PH Dropping. My setup included an air pump that was inside the grow tent with a CO2 fermentation canister. My PH continued to drop and I could not understand why. i later found that the CO2 enriched air from the tent was being pumped through the DWC res causing a acid rain like effect in with the water in the res.
The pump moved out of the tent this issue disappeared.

 

[Greenhorn_Greenthumb]

I’m getting the weirdest, but reliable, ph trends on res changes. I was chasing the ph and found that what I really needed to do is sit back and ignore the first 24-36hrs after a res change and then make any adjustments

for example…
new res comes in at like 6.7. I dont touch it
12 hrs later it’s at 7.1. I still don’t touch it
24 hrs later it’s at 6.8. looking better
36 hrs later I’m at like 6.3
48 hrs 5.7
60 hrs later 5.2. 4-6 squirts of ph up puts me around 5.7-6.3 for the rest of the week without touching it again at all and it holds pretty stable

im not sure what’s causing it, some nute or amendment im using? Something expire or go bad? Air stones? and for a long time I was chasing it and dumping in ph down in those first 24hrs and then just needing more ph up later. I was using a lot of ph adjuster.
sometimes those first 24-36 hours can be a little unsettling but trying to keep the ph adjuster in the res to a minimum I’ve found that I just need to ignore an initial ph swing after a new res change. And I’m glad I don’t have a doser set up, thing would have been pounding away at the ph down and I’d end up with like a 4.0 ph after it settled 48 hours later

 

[futurebanjo]

All things being equal, adding more fert will raise EC and lower PH at the same time.
You can add fresh water to lower EC and raise PH, so these are your best control levers.

PH+ and PH- addetives are more a last resort, and can cause massive swings, use them very carfully.

I've read a lot on here about staying 'in range' rather than trying to maintain a constant, and that makes a lot of sense to me, as in...

I've just dosed up my rez with ferts and water level, and i'm running EC 2.1 and PH 5.2 at the last reading.
So aside from topping up with fresh water, I'm gonna let the values drift naturally....
the ph will rise and the EC will lower, so if the EC gets too low (I'm 3 weeks in flower so I'm running the EC quite hot for a few weeks) I can just hopefully just add small amounts of fert, to bring PH down and EC up a bit back into 'range' as it were.

It's a balancing act, but there seems to be a lot of sense in allowing values to drift a bit within a sensible range, and most importantly, don't panick and do anything too extreme.

 

[ludeman]

I am somewhat new to growing and running RDWC with a combo of Jack's new RO and TAP formulas. It's hard to decifer all the info out there, there's a lot of bro-science but very little actual science. Luckily that is finally changing.
What I found most frustrating was the nutrient uptake/ph charts out there. So I drift my ph between 5.8-6.2 to optimize different nute uptake at different ph's.
What I've decided to go with is using aquarium dosing pumps for ph up/down for my tents. I can control them via an app and watch the results on my hanna ph/tds/temp monitor via cameras. So I have total control of ph anytime anywhere.
This was a much cheaper solution then auto dosing systems, plus no extra ph probes to calibrate and replace.
I also make my own up/down solutions with an eye on adding needed elements; sulfuric acid for soluble sulfer for ph down and potassium silicate (prepared properly) for silica for ph up.
This approach has worked very well for me but I'm no expert.

 

[rkymtnman]

potassium silicate (prepared properly) for silica for ph up.

out of curiousity, how do ensure that the KSil doesn't precipitate out of solution if adding it to a res with nutes in it already?

 

[Roguedawg]

ludeman that is some ingenuity you have come up with, i like that. Using camera to remotely monitor is genius.

 

[Roguedawg]

Ksil may not preciptate because of such a small amount at a time, i am guessing. He may have it diluted before it goes in res also.

 

[ludeman]

Ksil may not preciptate because of such a small amount at a time, i am guessing. He may have it diluted before it goes in res also.

Here is how Dr Bruce Bugbee does it

pH 11.3 Enhances the Solubility of Potassium Silicate for Liquid Fertilizer

Consistent delivery of up to 1 mM silicon (Si) to the root-zone is beneficial for plant health, but the maximum solubility of silicon is only 1.7 mM between pH 4 and 8. This makes Si difficult to concentrate and add through a proportioner in liquid fertilizer systems. The solubility of Si begins...

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