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Discussion Starter · #1 ·
I AM IN NO SUGGESTING OR RECOMMENDING THIS TO ANYONE!


This is in response to a question asked in another thread, people are curious why folks have so much difficulty altering the pH of their water with acid.

Indeed it is Alkalinity of which carbonate hardness KH, is a subset that resists (buffers) acid lowering pH.


  • When sufficient acid “overcomes” the KH, the pH drops.
  • The problem is that unless the carbonate is actually removed the “buffering” will return and the pH will return to its previous value.

Poor man’s alternative to RO as well as maintaining the general hardness (GH).

First is liming, many of us have seen this when dosing fertz containing Calcium, in fact it is the one point where KH and GH actually cross.



I have read many times about people saying it “snows” when they dose fertz. I resist saying anything as many “experts” like more complicated answers.



It is really Calcium bonding with the carbonate and precipitating, usually Calcium carbonate.


  • Effectively reducing the KH and not adding to the general hardness.
  • Industry uses this method to protect equipment, the
  • Calcium carbonate settles or is filtered out.
  • It is not difficult to reduce the KH in tap water using lime and maybe some heat.

The second method that I really do not recommend, but use myself, :icon_biggMuriatic acid, HCl.

Follow all the safety rules, serious do this out of doors, in a well-ventilated area, breeze blowing away from you. Use gloves, safety goggles, away from kids, pets so on. If you are a kid, get parental permission and supervision. The stuff can ruin your day (and life)!

I really recommend either being able to determine carbonate hardness accurately either by titration (some idea of chemistry) or a Lamotte test kit, still titration but the stuff is worked out for you. Be careful of even Hach’s and others have end points above pH 5. Make sure you have a reasonably accurate method of measuring pH.

The problem of pH returning, actually it is the carbonates reforming as with the liming above, we removed the carbonates from solution.


In this case we are going to drive the CO2 off the carbonate, effectively removing the carbonate from solution by aeration.

I would never dose Muriatic acid, HCl into my tanks directly, my critters are to curious and even well diluted I would fear the potential damage, damage that might not be immediately apparent.

Which brings the issue of pH swings, if your tank has critters, keep the

  • pH changes to no more than pH 0.3 per day.
    • In fact if you are changing the pH more than 1 whole point,
    • remember that a full point lower is 10 times more acidic
  • allow a couple days between the 0.3 drops in pH,
    • take your time.
  • Fish can be harmed and you may not see the results of the harm for a couple of weeks.
Large changes in pH can irreversibly harm fish,

  • the classic example are Neon tetras experiencing a full pH point swing,
  • even if the water is immediately stabilized and the fish keeper thinks he got away with it,
    • they all look fine, swimming around, eating but two-weeks later the tetras begin dying off and
    • within 3-days, a week, they are all dead.

For this procedure I recommend using a tub, garbage can (preferably new, at least clean:icon_wink), it is nice to have an air pump, capable of really getting the water frothing, moving. Glass air diffusers are better than stone or wood for this (my opinion anyway).

Determine how many dKH you wish to remove, frankly in my tub I usually aim for 1-dKH, figuring I will mix tap water to get the desired d-KH. Honestly there are situations to go under 4-dKH. Generally too much KH is not a problem, there are definite exceptions though.

Now, I have certainly learned that any mention of “moles” of something, “specific gravity,” “normalizing,” “molarity,” and so forth are a big turn off. So I am ripping off Dr. Randy Holmes-Farley.

Dr. Randy Holmes-Farley’s method seems awkward, but I get it. He uses Muriatic acid, HCl straight out of the bottle and refers to it as 11,000 meq/L, so he is seems to be asserting normal Muriatic acid is the 32%, 20-Baumé variety.


Be aware Muriatic acid is sold in varying concentrations so adjust accordingly.

Thinking of “acidity as negative Alkalinity” and since 1-meq/L will drop the KH 2.8-dKH

Figuring the water out of my tap is 12-dKH and


  • I wish to drop it to say 4-dKH, means
  • 12=dKH – 4-dKH = 8-dKH.
  • That is I want to reduce 8-dKH, or
  • 8-dKH ÷ 2.8 meq/dKH = 2.9 and
  • I operate in 20-gallon batches (my preference)
So:


  • (1-dKH/11,000-meq) × (1-meq Muriatic acid) × (2.9-dKH) × (3.8-L/1-gal) × 20-gal × (1000-ml/1-L)
  • = (1 ÷ 11,000) × (2.9 Muriatic acid) × (3.8) × 20 × 1000-ml
  • = 20-ml Muriatic acid


  • Add about half, 10-ml Muriatic acid in this case.
  • Aerate for a while, check the pH to see if it looks right.
  • Assuming things seem correct
  • add the remaining 10-ml Muriatic acid
  • continue aerating until you have blown off the CO2
  • once the pH has stabilized
    • (remember it will be rising as the CO2 dissipates)
  • change out enough water to lower the pH 0.3

It is actually less complicated than it sounds.

Joe
FBTB
 

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Very informative, thanks.


So if a person wanted lower KH, they just add a mild acid? I'm guessing the end result is a lower KH with GH being the same?

Would adding more Magnesium sulfate (Epsom salt) help as well? Doesn't Magnesium sulfate keep the calcium level from raising too much?
 

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Discussion Starter · #3 ·
Degas

Very informative, thanks.
So if a person wanted lower KH, they just add a mild acid? I'm guessing the end result is a lower KH with GH being the same?
Would adding more Magnesium sulfate (Epsom salt) help as well? Doesn't Magnesium sulfate keep the calcium level from raising too much?
You are welcome.

Well there is nothing mild about Muriatic Acid, but I get your meaning.
Yes, pretty much any acid, for instance you could use sulfuric acid, then aerate to blow off (degas as the gentry would say) the CO2.


You are correct this will not change the general hardness.
Adding Magnesium sulfate really shouldn’t do anything except add to the GH. In a sense the biggest problem with adding extra Epson salt is the laxative effect on the critters.


Technically any of the metal ions can precipitate out with carbonates; Iron (II) that isn’t chelated or chelated with glucose or even EDTA at somewhat higher pH would be an example.
Joe
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Nice write up Joe.

When using muriatic acid, is the chlorine a problem?

Liming I get. It’s been around for a long time and still used today. Btw, now you’re showing your age :icon_wink.

What I don’t understand was why dosing fertilizers causes’ calcium and carbonates to precipitate. We aren’t adding Ca so what is causing the reaction? Forgive my ignorance. I simply don’t get it.

Also, thank you for mentioning Dr. Randy Holmes-Farley. I’ve never heard of him. I searched for pertinent information about him and wow, what a wealth of knowledge!
 

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Discussion Starter · #5 · (Edited)
Anions, Cationsand Polarity... Oh My...

Thank-you.

Actually the chlorine really has no effect and the aeration tends to blow it off as well.

The “Calcium” we add is not the elemental Calcium (Ca) but an ionized form Ca⁺⁺ or Ca⁺⁺. The whole Ca⁺⁺ thing is why pure elemental Calcium is relatively rare. We dose Calcium compounds.

As an example when we dose Calcium chloride, which is really a compound made of three atoms, one Calcium ion, Ca⁺⁺ a “cation” with a formal charge of 2, and two chloride (ionized form of Chlorine) “anions each with a formal charge of 1 (negative), Cl⁻.

Because water is “polar” the Calcium chloride CaCl₂ is broken apart and now the Ca⁺⁺ is looking for another stronger bond and in our case manages to find (mainly due to the pH of our systems) a couple of Hydrogen carbonate anions (HCO₃⁻).

I am thinking of trying a bit better explanation but getting into equilibria of Hydrogen, carbonates, bicarbonates, and primary, secondary and tertiary phosphate ions is a bit much for now.

This is part of the complexity we face when trying to explain separate situations, the “snow” people see could be Calcium phosphate or any number of combinations of things.

I understand why people want simple, definitive answers, even if they are wrong and many retailers and manufacturers are more than happy to sustain the misinformation, but ultimately, facts need to win and facts do not care what we think or prefer.

I think Dr. Randy Holmes-Farley is one of the brighter bulbs and perhaps, along with the fact that reefers are always operating at the edge of the envelope, there is less tolerance for misstatement of fact in the saltwater tank world.

The Skeptical Aquarist is one of those places I always check before posting anything technical (controversial here) just to make sure I am not too far off.

Respectfully,
Joe
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I agree that the BB code be enlarged here. However, you can use HTML Entity (decimal) for unicode. Here is a good site that list them all. There is a HUGE number of them so I suggest writing your own list rather than searching every time.

Here is calcium with two superscript positive signs

Ca⁺⁺

This is what you have to type to see them (only in preview btw). Just remove the parentheses. I had to add those so you could see the code.

Ca&#(8314);&#(8314);

Example of an equation...

H₂O + Co₂ ⇔ H₂Co₃ ⇔ HCo₃⁻ + H⁺

versus this...

H2O + Co2 <--> H2Co3 <--> HCo3- + H+

and the code for the equation...

H&#(8322);O + Co&#(8322); &#(8660); H&#(8322);Co&#(8323); &#(8660); HCo&#(8323);&#(8315); + H&#(8314);

Edit: Here are a few to start your list. Remember to remove the parentheses

Subscript numbers...

C₀ C&#(8320);
C₁ C&#(8321);
C₂ C&#(8322);
C₃ C&#(8323);
C₄ C&#(8324);
C₅ C&#(8325);
C₆ C&#(8326);
C₇ C&#(8327);
C₈ C&#(8328);
C₉ C&#(8329);

Superscript numbers...

C⁰ C⁰
The HTML entity does not work for 1-3 here. You can use a keyboard shortcut though.
C¹ <-- Alt + 0185
C² <-- Alt + 253
C³ <-- Alt + 0179
C⁴ C&#(8308);
C⁵ C&#(8309);
C⁶ C&#(8310);
C⁷ C&#(8311);
C⁸ C&#(8312);
C⁹ C&#(8313);

Superscript charges...
C⁺ C&#(8314);
C⁻ C&#(8315);
 

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I'm not so sure that the Cl in HCl (muriatic acid) on its own will blow off with aeration. Cl2 (gas) can blow off, but as far as I know ionic Cl- will not because it is in the aqueous form. To blow off you'd need to remove an electron from one Cl- allowing the two to bind together to form a neutral gas.

If Cl- blew off then you'd expect table salt (NaCl) to blow off when mixed with water, but we all know that when you let a cup of salt water dry out you get the same amount of NaCl salt back afterwards (because the Cl- never left the water).

Will the Cl- convert to Cl2 by interacting with the carbonates in the water (the buffering system)?

Cl- can cause harm to plants and animals if it gets too high. I'd estimate a few hundred ppm, maybe a few thousand ppm Cl- is harmful depending on the species, so I suppose you have quite a bit of wiggle room.
 

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Discussion Starter · #8 · (Edited)
I know the answer is in here, somewhere...

Hi Zapins, All,

Good catch, when answering Zorfox, what passes for my brain was thinking the chlorine disinfectant in the water, completely missed the point.:redface:

I know I have an answer to the point about the chloride that however will require a dangerous journey to the inner reaches of my dilapidated brain.

Though just on the net amounts of chloride the dosing levels to remove or reduce 8-dKH will add about 82-ppm Cl⁻.

Respectfully,
Joe
FBTB

Bump:
I agree that the BB code be enlarged here. However, you can use HTML Entity (decimal) for unicode. Here is a good site that list them all. There is a HUGE number of them so I suggest writing your own list rather than searching every time.

Here is calcium with two superscript positive signs

Ca⁺⁺
Hi Zorfox,

Very cool, I actually think I know how to do that via MS Word, I will do some messing about.

I am sure if the swells that run this joint would just give up some of their jet-setting ways the BB and the environment would be much better off.:smile:

Respectfully,
Joe
FBTB
 

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Though just on the net amounts of chloride the dosing levels to remove or reduce 8-dKH will add about 82-ppm
Very cool. I'll keep it in mind. This is the first chemical method to remove KH that I've read about.

Have you tested it out yet?

82 ppm Cl shouldn't cause problems.

Bump: 82 ppm Cl shouldn't cause problems with plants, so we are safe on that front.
 

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Discussion Starter · #10 · (Edited)
Poor Mans RO... Sort-of...

Hi Zapins, All,

Yes, I have actually been doing this for 6 or 7 years, I rather hate to recommend it to general populations due to the potential for misuse or rather people who are not careful.

I think it is a great alternative to RO, especially when I wish to keep the other minerals.

I will say I have never considered anything under 140-ppm Cl⁻ maybe even higher particularly problematic. In fact I like to keep 40-ppm Cl⁻ minimum primarily for fish health, not sure that is anything I can prove, but it is what I do.

Respectfully,
Joe
FBTB
 

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I'm not so sure that the Cl in HCl (muriatic acid) on its own will blow off with aeration. Cl2 (gas) can blow off, but as far as I know ionic Cl- will not because it is in the aqueous form. To blow off you'd need to remove an electron from one Cl- allowing the two to bind together to form a neutral gas.

If Cl- blew off then you'd expect table salt (NaCl) to blow off when mixed with water, but we all know that when you let a cup of salt water dry out you get the same amount of NaCl salt back afterwards (because the Cl- never left the water).

Will the Cl- convert to Cl2 by interacting with the carbonates in the water (the buffering system)?

Cl- can cause harm to plants and animals if it gets too high. I'd estimate a few hundred ppm, maybe a few thousand ppm Cl- is harmful depending on the species, so I suppose you have quite a bit of wiggle room.
This is correct, you cannot evaporate/degas Chloride ions in water. Chlorine gas, yes. I had about 100 ppm or thereabouts, some folks have been using KCL at very high levels, a client of mine uses KCL to soften the Ca/Mg out of their entire house water, so the water is very briny coming in, most plants are find though as long as I add the Ca and Mg back. Chloride is about 150ppm.
 

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Discussion Starter · #12 · (Edited)
Aeration is the Key

Very cool. I'll keep it in mind. This is the first chemical method to remove KH that I've read about.
Have you tested it out yet?
82 ppm Cl shouldn't cause problems.
Bump: 82 ppm Cl shouldn't cause problems with plants, so we are safe on that front.
Hi Zapins, All,

I might add one of the reason Dr. Randy Holmes-Farley’s formula confused me a bit is the assertion that Muriatic acid is 11,000 meq/L out of the bottle. Years ago I thought I recalled the Muriatic acid I had was 20%. The stuff I use now is a 37% I get through a lab supply outfit. I tend to calculate the stuff based on its v/v molarity about 12M (12.06M actual) for my stuff as opposed to about 10.2M (I originally wrote 9.6M) for the 32% Muriatic acid referenced.

Everyone needs to remember the numbers I gave are based on the “normal” 32% (10.2M (I originally wrote 9.6M)) Muriatic acid.

I am doing it now with sulfuric acid, I am using some drain cleaner that appears to be about 96% sulfuric acid (18M), buying it as drain cleaner at the big box store is a heck of lot less expensive than buying from my lab supply guys, it will be tomorrow at the earliest before I have the results but there is no reason any strong acid shouldn’t work to reduce KH as long as it is well aerated.

Respectfully,
Joe

 

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Hi Zapins, All,

Yes, I have actually been doing this for 6 or 7 years, I rather hate to recommend it to general populations due to the potential for misuse or rather people who are not careful.

I think it is a great alternative to RO, especially when I wish to keep the other minerals.

I will say I have never considered anything under 140-ppm Cl- maybe even higher particularly problematic. In fact I like to keep 40-ppm Cl- minimum primarily for fish health, not sure that is anything I can prove, but it is what I do.

Respectfully,
Joe
FBTB
Joe, you recall the old toys that used vinegar and baking soda to cause them to move or the volcano experiments kids do/did?

Acetic acid is cheap and widely available and safe at the 5% level(white distilled). Baking soda is basically the KH in water.

So adding Vinegar would be a simple and safer method, and not that much difference in cost.

CH3COOH

Breaks down the KH in tap water also like HCL.

High M HCL and H2SO4 are both nasty stuff. Vinegar, something you eat and put on salad dressing. Both will do the same job.
I use to use H2SO4 at high M for cleaning diatoms, hated it, still do.
 

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Sorry for the confusion. I actually did mean chloride. Never the less question answered. Thanks.

I personally use white vinegar for mixing fertilizers. It's not only cheap but I usually have it handy. I honestly don't bother trying to change my PH anymore. It's too much of a hassle. If I can't grow something in my tap water it just isn't in my tank. Makes life much easier.

I still don't understand the "snow" issue. I understand the various forms of calcium. My question is how does adding fertilizers (KNO3, KH2PO4 and Plantex) cause this reaction. We're not adding calcium (any form) or carbonates. It's my understanding that it's the iron and phosphates reacting which causes this. If I'm wrong I really want to understand why.
 

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Discussion Starter · #15 · (Edited)
Worth It Or Not, Not for Me to Say

Hi Tom,

Certainly acetic acid will work, if I recall the objection to vinegar was not the acetic acid but the other organic materials that came along.

I think my post was inspired by the fact that a fair number of folks seem confused by the reason Muriatic acid and sulfuric acid in particular did not accomplish their goals.

My sense is that .89M acetic acid is more trouble than I wish to take. The final answer is without regard to which acid the answer is still aeration.

Worth the effort or not that is an individual decision, to me it is, for the tanks I desire a lower KH, since I moved from a place that had 12-ppm elk pee & 3-ppm bear pee, I have just had certain plants and fish that do not get along with what passes for water here.
************
Tom on a separate note, you ought to advise your clients to get a new water softener. Under ideal conditions they should be getting 76-ppm K⁺ for every 100-ppm of Ca⁺⁺ and Mg⁺⁺ removed and 0-ppm Cl⁻. All of the chloride should be out with the backwash.

Respectfully,
Joe
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Discussion Starter · #16 · (Edited)
Hmmm...

Hi Zorfox,

I will do a bit somewhere on ionic bonds and double bonds in a little bit, I have it mainly written I am just dealing with a little exhaustion and lawyers, which are doubly exhausting.

For now let us assume Tom’s clients water softener were working properly.

Most of what goes on in a water softener is like, your “snow” as a result of dosing fertilizers. An exchange happens a precipitate is formed, one bond is broken, and another is made.

In the case of the water softener, the resins allow the Sodium chloride or Potassium chloride to be held until the strength of the water combined with the greater attractiveness of the Magnesium or the Calcium releases a Potassium or Sodium (depending on KCl or NaCl) cation and bonds with the now free chloride anion, which still remains effectively attached to the resin. The resin in this case is acting as the filter to remove the undesirable hardness.

Then in a despicable act of environmental cruelty, the resin is backwashed, the brine released to be dealt with by sewage treatment folk, and the process repeated.

Respectfully,
Joe
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We have to factor in the dissociation properties of acids not just the pH (e.g. pK). Carbonic acid in coke makes it have a pH of 1, but its a weak acid (pKa of 6.7). HCL is much stronger and acetic acid is weaker again. Does anyone have an opinion of what factor dissociation has here for the objective? I don't think its an issue with acetic acid, as it will be over 90% dissociated at a pH over 5.

e.g. nitric acid is a weak acid (pKa of -1.3), and the conjugate base is nitrate. Anyone considered using this instead?
 

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Discussion Starter · #18 ·
Nice Try... Do You Want Me to Give the Answer?

Hi,

Actually we do not have to factor a dissociation properties. As a practical matter they are irrelevant, particularly the convenient method Dr. Randy Holmes-Farley’s formula provide. I love his “negative Alkalinity.”

Given that in no example are we attempting to overcome the acid-neutralizing capacity of solutes, in this case we are calculating an approximate amount of acid, using a molar-equivalent (meq) per liter to reduce a definite acid-neutralizing capacity (ANC). Then as a matter of procedure we use half or less of the acid to determine if we are on track.


For the heck of it you should not have too much trouble calculating it; all the relevant information is available.


Respectfully,
Joe
FBTB


We have to factor in the dissociation properties of acids not just the pH (e.g. pK). Carbonic acid in coke makes it have a pH of 1, but its a weak acid (pKa of 6.7). HCL is much stronger and acetic acid is weaker again. Does anyone have an opinion of what factor dissociation has here for the objective? I don't think its an issue with acetic acid, as it will be over 90% dissociated at a pH over 5.

e.g. nitric acid is a weak acid (pKa of -1.3), and the conjugate base is nitrate. Anyone considered using this instead?
 

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His work is focused on saltwater environments where hardness is usually a lot higher correct? Because of this, we need to factor in pK to our considerations in a freshwater environ, as the pH changes due to adding acids will be temporary and in the case of some acids reduce the dissolved oxygen dangerously.
 

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Discussion Starter · #20 · (Edited)
Phosphoric acids maybe

Hi,

In fact depleting oxygen would be one of the reasons for the aerating and never adding the acid directly to the tank, saltwater or freshwater. The greater reason is the chance of harming critters.

We can factor the pK, but it does not change the outcome when the reactions involve 20-ml of 9.6M HCl into 75-liters of water that will then be added to at least another 75-liters (assuming 50% water change).

The case of nitric or phosphoric acids, reducing certain buffering materials by less than an amount to significantly decrease pH could in a marginal system cause lowering, perhaps even significant lowering of oxygen, but given that most aquarium systems provide for transportation of water and introduction of air, gas exchange, so for an operating aquarium supporting life, I would see this as a minor concern.

This would be analogous to a lake or body of water undergoing eutrophication, low flow stagnation introduction of farm wastes or perhaps even “acid rain,” such an equivalent aquarium would in my opinion benefit from any water change as certainly the act of changing water would remove the organic materials that tend to add to greatly to the acid-neutralizing capacity, among the reason in the field we need to filter the water prior to testing for carbonate hardness or Alkalinity.

Among the problems I have seen folks having problems with their aquariums is having to get them in good enough shape that hobbyist test kits can be useful.

Respectfully,
Joe
FBTB
 
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