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Optimum PH.....

Hamster Lewis

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Found this on another board...seems like a petty good read. Will try and edit in the pics as well.

pH Management for Optimal Results by Andrew Taylor

Originally Located @ - Maximum Yield - Indoor Gardening

Optimum pH for nutrient solutions

For nutrients to remain dissolved and, therefore, available for uptake by roots, it is critical to maintain the pH between 5.0 and 6.0 with an absolute maximum of 6.5. When the pH of the nutrient solution is above 7.0, calcium, sulfate (and trace elements of copper, iron, manganese and zinc) can precipitate and become unavailable to the roots, causing plumbing blockages. High pH values, or those above 6.0, are to be avoided more than low values of 4.5 to 5.0. The effect of low pH upon the stability of nutrients is relatively insignificant.

The precise pH at which precipitation of macro-nutrients starts is determined by the combined concentrations of calcium and sulfate. Except for fertilizers low in calcium and sulfate this problem commonly occurs at pH 6.5 where the net* EC is 2.5 mS, or pH 7.0 for 1.5 mS solutions. Hence, to avoid precipitation, higher nutrient concentrations generally must be held at lower pH values. *Assume make-up water has nil EC.

In spite of this precipitation problem, some references advocate pH values well above 6.5 for some plant varieties, conditions that risk depleted concentrations of the above mentioned elements.
article556_01.gif

Figure one: Simplified illustration of how nutrient uptake effects pH of the nutrient solution


pH recommendation of 6.2 to 6.3?

Although 6.2 to 6.3 is a popular pH recommendation, which has no scientific basis. It appears to have gained mythological status from the early days of hydroponics when the only cheap means of measuring pH was the common ‘bromothymol blue’ pH indicator used for testing fish tank water. Interestingly, the lowest pH value able to be determined by that indicator is about 6.2. Hence, this value has unfortunately become an entrenched recommendation in some sections of the hydroponic industry.

Adjusting nutrient pH

The working nutrient pH should be checked at the following times:
When working nutrient solutions are first made.
After the addition of top-up water or additives, especially if they are highly alkaline.
In re-circulating systems, pH should be checked on a daily basis because the uptake of water and nutrients causes pH to change (figure one).
It is best to adopt a pH maintenance regime that prevents pH from getting too high. If pH is too high for a long enough period of time, the resultant precipitate usually cannot be re-dissolved.

article556_02.jpg
Figure two: pH indicators are useful for determining how much acid needs to be added to the nutrient reservoir.


How to minimize pH fluctuation

Use a nutrient brand that is highly pH buffered, particularly when using highly alkaline water.
Supply at least two gallons of nutrient for each large plant. Failure to do this will magnify pH (and EC) fluctuations, especially during hot and dry weather where water uptake and evaporation are excessive. Note, to avoid excess water uptake and evaporation; keep air temperature below 86oF and relative humidity above 50 per cent.
How to adjust pH

Step 1. Measure the pH: Use either a liquid pH indicator or an electronic pH meter (see sections below). Before measuring the pH, ensure that the nutrient is well stirred and that the sampling container is clean.

Step 2. Choosing a target pH: Note that it is inconvenient and unnecessary to hold pH at a single point value. Therefore, choose a target pH that minimizes the amount of pH maintenance:

Step 3. Adjusting the pH: Add a small amount of pH down or up product*. Then stir well and check pH. Repeat this process until the target pH is achieved.

*Important: Pre-dilute the dose into one quart (or at least 100 fold) of water before adding to nutrient, then rapidly stir the nutrient as you add this mixture. Failure to do this may cause permanent precipitation of essential nutrients. Also, if accidental overdosing to above 6.5 occurs, reduce the pH back to below 6.0 as quickly as possible using pH down.
ph ind.jpg
Figure three: This is the color range produced by a wide range pH indicator within the optimum pH range 5.0 to 6.5. Note the ease with which pH change can be detected.


Handy hints for adjusting nutrient pH


1. Add “high pH” (alkaline) additives before adding nutrient: Most additives will affect nutrient pH at least slightly. The best technique to adopt with those that elevate pH significantly is to add them to the water and adjust the pH down to 6.0 prior to adding the nutrient.

The less preferred but simplest alternative is to pre-dilute the additive in a separate volume of raw water. Then once this solution is added to the nutrient solution, quickly lower the pH to below 6.5. Note that a white cloudy precipitate (calcium sulfate) may form when the pre diluted additive initially merges with the nutrient solution. However, because the initial particle size of the precipitate is small, it will usually re-dissolve if the pH is immediately re-adjusted.

2. Do not pre-adjust pH of raw water: Note that the pH values being discussed here are the values of the working nutrient solution, not your make-up water. Unless your make-up water has a high alkalinity, do not bother attempting to adjust its pH prior to the nutrient being added. If you attempt this procedure you will typically get wild pH swings either side of the pH target without ever landing on the target value.

3. Estimating the volume of acid (especially for larger systems):
Step 1. Take a one quart sub-sample (or known volume) of working nutrient.

Step 2. Add a few drops of pH indicator (figure two ‘a’).

Step 3. While stirring this solution, measure the volume of acid required to turn this solution yellow – figure two ‘b’ (Yellow indicates a pH of 6.0 with most broad range liquid indicators).

Step 4. Multiply the volume of acid* by the volume of nutrient in your reservoir. That calculation will give you the volume of acid required to adjust the entire volume down to pH 6.0, for example.
Measuring pH with ‘indicators’

pH indicators are undoubtedly the simplest and most reliable method of measuring nutrient pH. Although they will not distinguish between, for example, a pH of 5.2 and 5.3, wide range indicators with good color resolution can be:
fast and user friendly
extremely accurate and reliable
economical
In comparison, pH meters require constant up-keep (i.e. cleaning, calibrating and correct storage), but even then may not give reliable readings.

pH indicators work on the principle that the color produced by the particular dye used in the indicator formulation is dependant on the pH of the solution (figure three).

Experience shows if you are aiming to adjust pH to 5.5 (orange) then an accuracy of +/- 0.2 is achievable. Because of their fundamental accuracy, reliability and easy of use, wide range pH indicators are the preferred method for measurement of pH in nutrient solutions. Note that pool and aquarium pH indicators are usually not suitable because unlike broad range indicators, they do not operate below pH 6.0.

fig4-2.jpg
Figure four: Thoroughly stir nutrient reservoir before sampling. Then leave the electrode in the sample for a few minutes before switching the meter on and taking the measurement. Do not immerse the electrode deeper than ~1 inch.


Taking pH readings


Step 1. Before measuring the pH ensure that the nutrient is well stirred, especially after pH up or down products are used. This is one of the most common mistakes made when testing pH (or conductivity). Also, ensure that the sampling container is clean.

Step 2. Using the sampling vial, remove a small sample of nutrient from the nutrient reservoir, add a drop of the indicator, mix, and then compare the final solution color with those on the colored reference chart (figure three).

Step 3. If the pH is not between 5.0 and 6.5, adjust it immediately.

Measuring pH with pH meters

pH meters employing a glass electrode are useful for precise pH measurement in nutrient solutions but require frequent calibration, proper storage and handling to ensure accuracy and reliability. The principle on which such meters operate is based on the fact that when glass of a certain composition separates two aqueous solutions having different hydrogen ion concentrations, a voltage is developed between the two faces of the glass. The electronic meter is simply a very sensitive voltmeter which measures that voltage but is calibrated in terms of pH units instead of volts.

Obtaining pH readings

Step 1. Make sure the meter is calibrated.

Step 2. Remove a ‘representative’ sample from the nutrient reservoir (figure four):
Stir the nutrient thoroughly prior to sampling.
Ensure the sampling container is clean.
Step 3. Rinse electrode in distilled water before immersing in the sample. Wait a few minutes before switching the meter on and recording the pH. Wait longer if the sample’s temperature is significantly different from 77oF.

Step 4. If the pH is not between 5.0 and 6.5, adjust it immediately.

Step 5. When complete, rinse the electrode with distilled water. Store the electrode in a proper storage solution when not in use.
 

Hamster Lewis

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Lemon Jack said:
Awesome find Hammy really helpful
Thanks LJ. I added the pics to it. I don't grow hydro but thought this was some interesting info.
 

Hushpuppy

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Thanks for looking out for us hydro-nuts there Hammy :) That is some good information. I will definitely hold onto that. :)
 

Hamster Lewis

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Hushpuppy said:
Thanks for looking out for us hydro-nuts there Hammy :) That is some good information. I will definitely hold onto that. :)

Glad I cld help you hydro guys.....I like to dabble in hydro every so often myself. This explains some of the problems I hve experienced with ph drift in hydro.
 

Reverend Raymondc

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right on the ph...first time for me and I have seen the swing in the ph..I ph my water for 24 hrs the check the readings then add my nuts, the recheck 24hrs later then do my plants..ph stays at 6.... for 7 days then I redo it all over again...working for me..
 

zardoz

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The proper way is to mix your nutes and water first THEN adjust your ph... NOT adjust your waters ph then mix nutes...


z

Reverend Raymondc said:
right on the ph...first time for me and I have seen the swing in the ph..I ph my water for 24 hrs the check the readings then add my nuts, the recheck 24hrs later then do my plants..ph stays at 6.... for 7 days then I redo it all over again...working for me..
 
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I also always add nutes before pHing. I don't understand pHing your water and then adding nutes as the nutes will change the pH of the water. Your initial adjustment would be a guess at best and you are almost certainly going to have to readjust your pH.
 

trillions of atoms

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Always add nutes, let buffer overnight then check.... Ph still to low? Nutes could be to strong... Ph still to high? Nutes could be weak. If ratios are right and still have to ph?? Nutes suck!! Lol. Proper nutes you should not have to ph right away or for days even.


I've noticed when plants are young and not feeding as much I have to ph more often.... When they get bigger and drink more .. The nutes concentrate and help buffer ph better. I usually add water on the fourth or fifth day, then check TDS and add ratio to bring TDS back over 1100-1300. Once over 1000 ppm of nutes GH will always buffer down to the proper range and hang there.


FYI from my exp running ebb and flow with GH nutes and a slightly tweaked Lucas formula....
 

trillions of atoms

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Biggest thing is TO KEEP YOUR PH METER PROPERLY CALIBRATED.... If you start to notice crazy PH readings all of the sudden... IT'S PROLLY JUST YER PH METER OUTTA WACK!!!!!!!
 

Greenman

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What can you add to lower ph? I know the ph up and down solutions, but is there anything else that will work? What about vineagar? Or citric acid , like what's used in wine making? Can these organic acids do the job ? My tap water is a high ph of 8.5
 

Hushpuppy

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You can add stuff like vinegar or citric acid and it will work but the problem with these "organic" pH adjusters is that they aren't as strong and will not stay in the solution as long. Plus they add new things to the environment that can create issues sometimes. Now if you can find straight powdered citric acid, that may work.

But I don't think it really matters if you use chemical pH adjuster as it is usually derived ffrom natural stuff and is used in such small amounts that it doesn't add anything to the environment. Technically you could use sulfuric acid in diluted solution as it is derived ffrom sulfur which is one of the micro elements needed in the grow. :)
 

pitviper

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organic food type(vinegar,citric acid)will wreak havoc in a chemical solution,as they rapidly decompose and will add muck with very undesirable live plant killing bacteria to the nutrient.also as posted above,battery electrolyte(sulphuric acid)works great also,it last longer, more stable,less expensive than any commercial hydro down that I've ever used.
about eight dollars per quart will last you many dozens of grows as you really use or need very small amounts,and the plants dig it.and you can purchase it at most auto parts stores.
 

hippy59

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I am building my own DWC 5 gallon 5 bucket system. I have grown in dirt mostly and about the last 3 years in cocoa, which I enjoyed and learned a lot. In my 40 some years of growing and having fish I have noticed that my PH will not stay down after I PH my water. I must PH almost daily for months till I break that PH barrier for my new fish tanks. so it will be the same thing for my DWC system. that's why the 5 buckets. I have looked at a lot of DWC, RDWC and UF( underflow?)DWC systems, all of which eather suck, is overkill, for what I want or just way way to expensive. so I build my own.

sorry I babble most of the time. lol. amyway I don't see how PHing my 1 " resevroar " bucket is gonna help with the other 4 buckets, that are all aligned in a c shape or even an o shape. the plants don't eat that much water. so I am thinking of just buying a very small pump to kind of give it a very small flow from my resevroar bucket to the number 5 or end bucket. I am not really interested in top feeding my plants as this is no longer DWC but more like a drip system.

how is everyone else PHing in DWC without lifting the plants out of the buckets all the time?
 
P

P Jammers

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I am building my own DWC 5 gallon 5 bucket system. I have grown in dirt mostly and about the last 3 years in cocoa, which I enjoyed and learned a lot. In my 40 some years of growing and having fish I have noticed that my PH will not stay down after I PH my water. I must PH almost daily for months till I break that PH barrier for my new fish tanks. so it will be the same thing for my DWC system. that's why the 5 buckets. I have looked at a lot of DWC, RDWC and UF( underflow?)DWC systems, all of which eather suck, is overkill, for what I want or just way way to expensive. so I build my own.

sorry I babble most of the time. lol. amyway I don't see how PHing my 1 " resevroar " bucket is gonna help with the other 4 buckets, that are all aligned in a c shape or even an o shape. the plants don't eat that much water. so I am thinking of just buying a very small pump to kind of give it a very small flow from my resevroar bucket to the number 5 or end bucket. I am not really interested in top feeding my plants as this is no longer DWC but more like a drip system.

how is everyone else PHing in DWC without lifting the plants out of the buckets all the time?
If your PH is not stable you have either too much food or not enough. Too much food and your PH will drop. Not enough and it will go up dramatically.

That said you want to have your PH rise about 1/2 a point per day when your dialed in on a ramp growing in hydro.

I also run fish tanks both salt and fresh, and it's all about having natural buffers to keep PH stable. I do weekly water changes, so would have no idea how you go months to get a tank stable??

Best of luck with that DWC. Best design for the tweaker ever. :)
 

sopappy

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I also always add nutes before pHing. I don't understand pHing your water and then adding nutes as the nutes will change the pH of the water. Your initial adjustment would be a guess at best and you are almost certainly going to have to readjust your pH.
First time: Water, add nutes, adjust pH, (note amt Ph up or dn used)
thereafter: Water, adjust ph (you know how much to use), add nutes
 

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