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Ph Upswing using PF and Autopots Is this normal?


Grant
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Hi Guys 

I am currently using powderfeeding for the first time in RO water with added Calcium and hybrid PF, my ph keeps rising from 5.6 to 6.2 in 24 hours after filling the res.

I am not using a airstone in the res, ppm stays stable but ph fluctuates, ph meter is calibrated, coco, hydroton and perlite mix. but as this system isnt recirculating I cant find reason for ph jump.

Please help

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  • 4 weeks later...

Shouldn't be a problem at that range tbh may be get a little nuts burn but not going to cause much probe. I wouldn't worry. If it's bugging you just use some ph down but I'm a hydro guy that's done many hydro and ph jump like that is common. I think the plants eat the food and it causes ph to go up or may be a simple heat change but like I said I wouldn't worry. If it goes over 6.5 then re calibrate you ph pen to be safe and just ph down. Could also be your water and nuts, like u may have hard water but your nuts for soft or vise versa. I wouldn't stress about it.

The biggest killer of weed is over loving them ;)

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Adding a bubblestone or two is always a good idea if you work with feeding solutions longer than a few hours and mandatory for any hydro imho.

 

The smaller your reservoir the faster EC and especially PH drifts away, this is normal. Keep it in the demanded range and the smaller the conatiner the more

often you have to correct it and eventually, after 3-4 days, drain it and renew it. With larger reservoirs you can go up to 5 days with the solution ( with activly bubbling airstones then )

if you have a fairly large container for your plant.

 

Large is when you would not have to refill it by volume abd it would survive at least 5-7 days. Small is a container/system where you have to refill every other day before the system

stops working. I suggest at least 3 days volume as reservoir size to somehow keep the PH rollercoaster under control the easy way.

 

Measure your water's PH and EC from tab,    ec below 0.4 is rather soft, above 0.5 is considered hard water ( more solids solved ).

 

Soft water tends to respond faster to any changes in the solution with PH changes than harder water.

 

It takes a lot more acid to change PH in hard water than it does in soft water, it also takes more of anything in hard water to respond.....in general...

 

Fim

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  • 2 weeks later...

I can't find reason for ph jump.

I'd just add that ph fluctuations are normal with hydro and FIM covered how to minimize them. It is also why you need to check it often or else things can go bad real quick.

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Let me explain why PH and EC change with time. I would not call it fluctuate cause that would mean up and down wildly, it usually only goes one direction usually if all is within normal parameters, which is volatile enough as you will see.

 

Let's start with PH value fierst, what is that ?   Simplified, PH value is electro negativity of a water based solution, very similar to what EC value represents and de facto is co-related.

 

Tab water, there is soft and hard tab water. The softer it is the less minerals and Ions are dissolved. All of them act as a kind of PH stabilisator. Soft water is more likely to respond

quickly to changes in the solution with PH changes, for example contamination with tiny rests of dirt, soap, whatever. Softwater will react more intense with PH changes than harder water would.

 

Now comes the fertilzer.

All fertilzers ( should ) contain one or more forms of PH stabilisator/buffer that will compensate PH drifts to a certain degree over a certain time span.

So when you mix a new solution with PF for example, it is good to go for 5-10 days, depending on temperatur, airstone yes or no and other factors.

 

Once you pour the solution into your res with Hydro the plant will start to absorb "SOME" of the ingredients of your solution but never all of them in the same relation ( quantity wise ) as

their are dissolved. This uneven uptake of electro negative solids out of the solution is one factor of why the soup changes over time.

Another factor is the lifetime of added PH buffers from the fertilizer. I have no insight on the chemical site of these substances but basically they have to release new electro negative

particels out of some cumbersome molecule that otherwise doesnt harm the whole thing ( might be completetly wrong here ). At some point those molecules are used up and you will

eventually have to exchange the solution or work even harder to keep it in it's boundaries. Adding more and more acid is not the way to go, exchanging after max 5-7 days is better.

 

The role of DWC typical hauntings like slime etc. do their own part of mixing up the PH scale. Whastever you put in the water to prevent this might very well change the PH on its own.

 

I am no fan of DWC as it has no dry cycle and slime and such needs special attention....causing a whole rat's tail of problems I am not willing to accept for now.

 

If you do DWC you have to be precise and reliable in checking all that. If you feel like that is not your way then you might be better off with a grow style that is not as demanding

and control sesnitive as SOME hydro is. There are Hydro systems that have less problems with PH, aka Coco pots or Drain-2-Waste setups.

 

I think I have shown you way this happens, so you can accept it as a fact, as a nature of the beast and not your mistake is most cases.

 

Check PH twice daily until you get the feeling, then still check it twice or it will catch you sooner or later :)  DWC is a pain imho unless you sleep next to your setup.

 

Grow with style, go soil :)

 

Fim

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Thanks FIM for typing all of that as I didn't want too. LOL :fan: You also talked about reservoir size but didn't say how it and evaporation can also affect ph and that's why bigger is better as well as all the other reasons you mentioned. I've seen wild fluctuations in others setups that used an undersized reservoir and I just thought it was caused by the uptake of nutrients that raised the ph followed by a quick rebound back down as the water evaporated. If your medium has any ingredients that can change the ph as they break down, like coco does, than that can also affect ph. I think you also mentioned to check ph before and after it cycles through the first time and I have seen crazy differences when checked before and after the cycle and then the next day. I never tried to figure out the cause because I knew the reservoir was way to small and the larger one fixed the problem.

 

And I second the soil suggestion. :fans: 

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Thanks for typing all of that as I didn't want too. LOL :fan: You also talked about reservoir size but didn't say how it and evaporation can also affect ph and that's why bigger is better as well as all the other reason you mentioned.

 

And I second the soil suggestion. :fans:

 

 

 

Oh...easy:  The res size matters a lot in HOW FAST it ( the solution ) responds to changes due to plant(s) uptake. The larger the res the less particles are missing in the overall quotatioj and thus the change is lower with the same amount of uptake in a larger res compared to a smaller res. Sounds logical ?

 

Hell yes, put a damn lid on that barrell. Evaporation should not happen while in res but does occur while the solution cycles in the system. depending on the system setup it may be very small or to an extend where it will matter. What happens is, your solution gets STRONGER as only H2O evaporates. Keep this n mind on hot days, lower EC by 0.2 or .3.

 

The rest, and this above, is common sense. Sometimes it helps to just lean back and let the brain do it's work while you think about things how the interact, they all do, and  make your momentary conclusions. They change over time and get more complete, just dont stop tracking the ball :)

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What someone should do that I have never seen before is make a grow journal post about their hydroponic nightmare with pics of all the slime, root rot, algae, stunted growth, hose popping off flood creating, total plant death nightmare!!! :banghead: 

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