adjusting the PH

[David Waite]

Hello fellow fish huggers. My well water is at 8.0 . Has anybody use a acid they recommend for lower the PH. My system hasnt been run yet as it is in its final stage but the water is sure is high for starting off. My system is 1000 gal so an economical option would be great.

[TCLynx]

There was some guy that bubbled CO2 into a system to adjust the pH but I don't think that was very cost effective.

 

I expect some diatomite in a bag in the top up tank might help against the natural tendency of the well water but that would require some testing and I'm not sure how fast acting the diatomite would be. 

 

Would be interesting to find out though.

[Jim Logios]

I just started a system, and the ph is up around 8.  I spoke to a woman I work with who heads up the "Trout In The Classroom" program at the school I work at.  I asked her what she uses to lower the ph, and her answer was "sticks".  Sticks I asked... what kind of sticks?  The wooden kind she replied... a few small dried branches from a hardwood tree such as Oak or Hickory.  Apparently, tannic acid is naturally in them, which makes for a cheap (if not free) solution.

 

Anyone ever try this?

[TCLynx]

I did use wood chips as a trial in a system once.  Beware that tannic acid will also color your water and may only be partially effective at bringing your pH down depending on why it is high.

 

There are two very common causes of high pH.  First, you source water is heavily buffered, like mine comes from a limestone aquifer.  Second, you used limestone as your media or some other material in your system is a strong carbonate buffer.  I have a system with lots of shells mixed into the media and that system rarely sees a pH below 7.6. 

 

If you have a media that buffers your pH, there is no point in adding acid to bring the pH lower than the natural buffer level, that would only cause pH bouncing and be bad for everything involved.  That system I tried using the wood chips to offset the pH buffer of a bed full of shells, didn't work.  Turned the water really brown (couldn't see fish) but the pH was still not lowered below the natural buffer level of the shells which is 7.6.

 

If your high pH is because of the source water, then it is possible to adjust the pH down using acid until you use up the buffer capacity of the water and at that point you will either need to top up with the high pH water to help keep your pH from dropping too low or add some buffer back in at very small quantities to keep the pH from crashing below the range of functional bio-filter bacteria.

 

Perhaps it would be possible to adjust the pH of your source water using sticks but I'm not sure how to go about doing it or how quick it would work or if you want the water to change color that much.

[Jim Logios]

Thanks TC.  Not sure if my water is "buffered" or not.  I am on a deep well (300+ feet) and the water is good quality, and tasty.  I know it's on the acidic side since I have copper pipes inside the house that  paints my bath tub "copper green".

 

My media is hydroton.  Not sure if it's alkaline or not, but if so, that's probably the reason for the high ph.  Anyone know if hydroton is alkaline?

 

TCLynx said:

I did use wood chips as a trial in a system once.  Beware that tannic acid will also color your water and may only be partially effective at bringing your pH down depending on why it is high.

 

There are two very common causes of high pH.  First, you source water is heavily buffered, like mine comes from a limestone aquifer.  Second, you used limestone as your media or some other material in your system is a strong carbonate buffer.  I have a system with lots of shells mixed into the media and that system rarely sees a pH below 7.6. 

 

If you have a media that buffers your pH, there is no point in adding acid to bring the pH lower than the natural buffer level, that would only cause pH bouncing and be bad for everything involved.  That system I tried using the wood chips to offset the pH buffer of a bed full of shells, didn't work.  Turned the water really brown (couldn't see fish) but the pH was still not lowered below the natural buffer level of the shells which is 7.6.

 

If your high pH is because of the source water, then it is possible to adjust the pH down using acid until you use up the buffer capacity of the water and at that point you will either need to top up with the high pH water to help keep your pH from dropping too low or add some buffer back in at very small quantities to keep the pH from crashing below the range of functional bio-filter bacteria.

 

Perhaps it would be possible to adjust the pH of your source water using sticks but I'm not sure how to go about doing it or how quick it would work or if you want the water to change color that much.

[TCLynx]

Hydroton should be pretty pH inert. 

 

I don't know if it takes acidic water to turn copper green.

 

I would recommend collecting a well water sample and do a pH test on it right away then save a sample and leave it to air out (through an air stone in it if you have an air pump available) for a day or so then run another pH test.  Water right from the well or holding tanks can have a false low pH because of dissolved carbon dioxide trapped in the water acts as an acid but once that carbon dioxide escapes into the air the water could have a far higher pH.  I didn't know this when I first started doing hydroponics and it caused me no end of troubles.  I couldn't figure out why adding my tap water with a pH of 7 would cause my hydroponic nutrient to be up at a pH of 8 the next day!!!!!!  Now I understand that the pH reading on my tap water was being messed up by the dissolved carbon dioxide and that my tap water was really up over 8 most of the time.

[Izzy]

Oh God... you guys are really something... LOL

 

Anyway, this describes the quantitiy needed for a 1000 gallon system if you use muriatic acid (hydrochloric acid).  I will copy and paste for those that can't navigate freely.  Proper pH Down Dosage

 

1 gallon of HCl @ 38% concentration weighs 9.901 pounds.
1 mole of HCl  weighs 36.5 grams.

Weight conversion:
9.9 lbs * 2.2 kg/lbs = 21.8 kg

HCl weight conversion:
21.8 kg * 38% = 8.3 kg
8.3 kg * (1000 g / 1 kg) = 8300 g of HCl

Grams of HCl per Liter:
(8300 g / gallon) * (1 gallon / 3.78 Liters) = 2196 g / L  [which is 2,196,000 PPM for the curious]

Moles per Liter:
2196 g * (1 mol HCl / 36.5 g) = 60 moles of HCl per Liter

60 moles of HCl per Liter

HCl is a strong acid, meaning that it will disassociate 100% in a solution.  We also know the pH of a solution of 7 is 10^-7 moles of H+ per Liter.  Therefore, 1 mole of HCl will lower 10,000,000 Liters of a solution of pH 8 or high to roughly pH 7 (roughly meaning +- 0.1 pH).

So, for 4000 Liters we would need roughly...

(1 mol / 10000000 L) / (4000 L)  = 0.0004 moles of HCl

(0.0004 moles of HCl / 60 moles of HCl) = 6.7 x 10^-6 % of 1 Liter or 6.7 mL of the solution per 4000 Liters (roughly 1000 gallons)

So, for every 1000 gallons add 6.7 mL of 38% HCl (Muriatic Acid).  If your local store only carries 10% use about 25 mL of 10% HCl (Muriatic Acid).

Please review this acid safety before beginning any work unless you are a professional: SAFETY PACKET

SAFETY GOGGLES AND GLOVES ARE A MUST.  I do not work without these, at a minimum (depends what I am doing).

10% is far safer and more commonly available, but still observe safety and caution.  Always add acid to water and never the other way around (even for low concentrations).  NEVER work indoors with this stuff unless you have a fully equipped laboratory to work in (again, even with low concentrations for safety's sake).

SPECIAL NOTES
A buffer occurs when a molecule has speciation at different pH values.  This happens because the molecule might grab 1 hydrogen ion at one pH and as you move through the pH levels it might grab 2, or 3, or 4.  The amount of speciation a molecule will exhibit is indicated by it's pKa value.  This can be looked up and calculated easily, but you would have to know EVERYTHING in your water.  A quicker approach would be to put just enough in the water to get the expected pH value and wait 24 hours.  After everything settles, take another reading.  From there you can adjust accordingly.  For future reference, you will know what your system roughly takes to adjust if you have to do a full water change or you can calculate the volume ratios and have that on hand!

ECONOMICAL NOTES
$5 worth of this stuff will treat hundreds of millions of gallons.  :ugeek:

DANGER TO FISH?
Obviously, HCl will leave Chlorine in your water, but the toxicity for fish is millions of times higher (in this case 10 million) than the concentration of Chlorine we are adding.  Also, it will volatilize OUT OF THE WATER within a few days.  No worries there.

Sample MSDS
http://www.brown.edu/Departments/Visual_Art/documents/Muriaticacid.pdf
http://www.sciencelab.com/msds.php?msdsId=9924285

It is unlikely there will be anything extra in your solution because HCl is VERY reactive.  However, always verify with your supplier and check the MSDS or have me check it for you if you have any doubts.

 

 

[Izzy]

Oxygen turns copper green not acidic drinking water.

Jim Logios said:

Thanks TC.  Not sure if my water is "buffered" or not.  I am on a deep well (300+ feet) and the water is good quality, and tasty.  I know it's on the acidic side since I have copper pipes inside the house that  paints my bath tub "copper green".

[Izzy]

This would essentially be useless, if not worse.  As you aerate your water you would be volatilizing (off gassing) the carbon dioxide in the water.  Carbonic acid is a weak acid.  Carbonates would not spontaneously be made in the water... in order for them to be made there needs to be a chemical reaction WITH something else, you don't just magically get carbonates or bicarbonates... and if so, what exactly is the concern here?

 

As someone said, this is also a bad idea from an economical standpoint.

 

From a biological standpoint, acute carbon dioxide toxicity can kill many different organisms from fish, bacteria, to plants.

 

Kobus Jooste said:

Here is a different thought line to explore.  You can make a weak acid - Carbonic acid (H2CO3) by bubbling CO2 through your water.  Anyone try this before?  Not sure what the total effect of this process will be, as you are potentially loading the water with extra CO2 as well as potentially creating carbonates and bicarbonates.  A water chemistry expert will probably be needed to highlight the potential issues.

[Izzy]

You will get the opposite effect.  Shells are usually 90% or more calcium bicarbonate.  You can google that, but you will see it will act to absorb hydrogen ions thereby raising your pH not lowering it.

 

Silica sand is Silicon Dioxide and is extremely stable and macromolecular.  It will not break down into new compounds readily.  This substance would be closer to pH inert.

 

Kobus Jooste said:

I'm about to start experimenting with silica sand / shell grit to see what it does to the system.  My pool shop told me not to dump used pool filter sand in the garden as it will acidify the soil - I'm interested to see if it will do anything to water though.  Will let you know.  In the past, I used to pre-balance alkaline pond water with nitric acid in a seperate drum before adding it to my AP system at a nursery.  Not sure if you want to have to keep on adjusting your top-up water though.

[Kobus Jooste]

Why thank you for setting the record straight in such a dignified, diplomatic way.  What would we ever do without people like you Izzy?  I dare you to speculate a bit outside your field of training in stead of pitching up once in a while to spew scorn at people who dare do this.

izzy said:

This would essentially be useless, if not worse.  As you aerate your water you would be volatilizing (off gassing) the carbon dioxide in the water.  Carbonic acid is a weak acid.  Carbonates would not spontaneously be made in the water... in order for them to be made there needs to be a chemical reaction WITH something else, you don't just magically get carbonates or bicarbonates... and if so, what exactly is the concern here?

 

As someone said, this is also a bad idea from an economical standpoint.

 

From a biological standpoint, acute carbon dioxide toxicity can kill many different organisms from fish, bacteria, to plants.

 

Kobus Jooste said:

Here is a different thought line to explore.  You can make a weak acid - Carbonic acid (H2CO3) by bubbling CO2 through your water.  Anyone try this before?  Not sure what the total effect of this process will be, as you are potentially loading the water with extra CO2 as well as potentially creating carbonates and bicarbonates.  A water chemistry expert will probably be needed to highlight the potential issues.

[Izzy]

What is a buffering agent ?

Buffering agents can be either the weak acid or weak base that would comprise a buffer solution.

 

Wikipedia - Buffering agent

 

Okay guys, so buffering agents basically have to do with the pKa value and the speciation caused therein by chemical interaction.  It's not very difficult to understand, but requires a little chemistry background.  The most common buffering agent in aquaponic systems is ammonia.  I hope that helps give you an idea...

TCLynx said:

Uh, well I don't know of any "buffering agent" that would work opposite since buffers usually work to bring pH up if it drops below a certain point.

[Izzy]

I don't know what your problem is, but I am just trying to help...  There is a lot of FOLKLORE in the aquaponic community.  My only wish is to clear it up.  If you do not want my help, I will withhold it happily as to avoid heartache.  I have helped thousands of people in different areas of aquaponics and horticulture, but I have never been met with contempt as I have from you, repeatedly, and only in this community.

 

Also, I don't quite understand what you mean to speculate outside my field of training...  Chemistry is a science with a long history of experimentation.  Any first or second year college student should be able to make exactly the same claims I have made.  I am only presenting sound scientific fact, which I do not care to question as these fundamental concepts have been tested and retested and commonly accepted for almost a hundred years, sir...

Kobus Jooste said:

Why thank you for setting the record straight in such a dignified, diplomatic way.  What would we ever do without people like you Izzy?  I dare you to speculate a bit outside your field of training in stead of pitching up once in a while to spew scorn at people who dare do this.