Liquid KH dosing - The Planted Tank Forum
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post #1 of 13 (permalink) Old 05-06-2016, 04:59 AM Thread Starter
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Question Liquid KH dosing

Hi,

Who can think of a way to dose liquid KH or alk buffer using a dosing pump?

It's easy to find solutions (no pun intended) for marine tanks OR powders for fresh water tanks. But I've not found a liquid product for fresh water.

My tap water is 1KH so I need to dose alkalinity buffer, or kh+, into the tank to prevent gradual decline in PH.

I use a fully automated water change system & auto top off system so I'd love to integrate a liquid KH/Alk dosing using my peristaltic pumps.

Ideally this liquid would not be phosphate based.

Any ideas?

Thanks in advance!
Andrew
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post #2 of 13 (permalink) Old 05-06-2016, 05:05 AM
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You can mix this powders with RO water and then add it in this form. That's how I've been doing it for a long time now. Only problem is you need to shake or mix it every time.


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post #3 of 13 (permalink) Old 05-06-2016, 05:28 AM
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Not familiar with auto dosing systems, but you can use Potassium (Bi)Carbonate to increase KH.
If the system automatically does water changes, that should take care of the normal gradually decreasing pH though?
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post #4 of 13 (permalink) Old 05-09-2016, 07:46 PM
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Quote:
Originally Posted by WaterLife View Post
Not familiar with auto dosing systems, but you can use Potassium (Bi)Carbonate to increase KH.
If the system automatically does water changes, that should take care of the normal gradually decreasing pH though?

Would kh2co3 be preferable over k2co3 for raising KH?
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post #5 of 13 (permalink) Old 05-09-2016, 08:19 PM
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Originally Posted by nilocg View Post
Would kh2co3 be preferable over k2co3 for raising KH?
3.6g Potassium Bicarbonate (KHCO3) in 100 litres (26.417 US Gallons) of water will raise the dKH by 1

2.4g Potassium Carbonate (K2CO3) in 100 litres (26.417 US Gallons) of water will raise the dKH by 1

Either would work. Would depend on what prices you could get either for as to which would be more cost effective. For me, on eBay, I could get Potassium Carbonate for the same price as Potassium Bicarbonate, so I just get Potassium Carbonate, which would treat more gallons/raise more KH, by weight.

Though, maybe some might prefer the smaller KH increments that would be easier to measure out with Potassium Bicarbonate?

Cheers
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post #6 of 13 (permalink) Old 05-09-2016, 08:23 PM
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Originally Posted by WaterLife View Post
3.6g Potassium Bicarbonate (KHCO3) in 100 litres (26.417 US Gallons) of water will raise the dKH by 1

2.4g Potassium Carbonate (K2CO3) in 100 litres (26.417 US Gallons) of water will raise the dKH by 1

Either would work. Would depend on what prices you could get either for as to which would be more cost effective. For me, on eBay, I could get Potassium Carbonate for the same price as Potassium Bicarbonate, so I just get Potassium Carbonate, which would treat more gallons/raise more KH, by weight.

Though, maybe some might prefer the smaller KH increments that would be easier to measure out with Potassium Bicarbonate?

Cheers
Ya I understand that part of it, but I just see most people suggesting the bicarbonate form. Maybe its more readily available?
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post #7 of 13 (permalink) Old 05-09-2016, 08:53 PM
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Originally Posted by nilocg View Post
Ya I understand that part of it, but I just see most people suggesting the bicarbonate form. Maybe its more readily available?
I'm no expert, but I believe they would both be equally soluble?
Carbonate compounds always turn bicarbonate (HCO3-) in solution, which is soluble in equilibrium with CO2.

Identical to Baking Soda (Sodium Bicarbonate) vs Baking Powder (Sodium Carbonate), in this case, I believe the Bicarbonate form is much cheaper to get, but both are still suggested to work in the same manner (carbonate being more "potent" by weight). Though I have heard you can bake Sodium Bicarbonate and it will turn into Sodium Carbonate? I'm no chemist, so I can't confirm or deny.

If I am mistaken, please let me know. I believe @Diana also has experience with using Potassium Bicarbonate, maybe she knows more between the two?
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post #8 of 13 (permalink) Old 05-10-2016, 07:17 AM
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No, I believe bicarbonates are generally more soluble than carbonates.

Bicarbonates tend to be more readily available than carbonates (not sure about pricing). With regards to the "potency" I did not work out the molar concentrations, but this is an exercise left to the reader (or you can just Google it).

Yes, baking sodium bicarbonate will decompose it into sodium carbonate.

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post #9 of 13 (permalink) Old 05-10-2016, 11:05 AM
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Originally Posted by Darkblade48 View Post
No, I believe bicarbonates are generally more soluble than carbonates.

Bicarbonates tend to be more readily available than carbonates (not sure about pricing). With regards to the "potency" I did not work out the molar concentrations, but this is an exercise left to the reader (or you can just Google it).

Yes, baking sodium bicarbonate will decompose it into sodium carbonate.
Thanks for the reply Darkblade.

Could you do the same, baking Potassium Bicarbonate to create Potassium Carbonate?
Again, I'm no chemist so I have no idea if anything is ignitable or if the same would apply (I would imagine so).

Found these about solubility
INTRODUCTION TO CHEMISTRY OF CARBONATES & BICARBONATES
https://en.wikipedia.org/wiki/Calciu...ate#Solubility

Too tired to read them right now, so will get back to that later.
Does it state anywhere the solubility of how many grams of bicarb vs carb can be dissolved in X amount of water?
Just from knowing that dissolved form would only be bicarbonates, wouldn't they have the same solubility?
Lol, I need to get some rest and research it.
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post #10 of 13 (permalink) Old 05-10-2016, 02:01 PM
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Yes, in this case, the cation does not matter when it comes to decomposition process.

Regarding solubility, gram weight is nice, but an incorrect way to compare the two; you need to look at molar amounts that can be dissolved. Alternatively, you can look at solubility constants.

Bicarbonates are more soluble than carbonates though (I just did a quick calculation).

Quote:
Originally Posted by WaterLife View Post
Thanks for the reply Darkblade.

Could you do the same, baking Potassium Bicarbonate to create Potassium Carbonate?
Again, I'm no chemist so I have no idea if anything is ignitable or if the same would apply (I would imagine so).

Found these about solubility
INTRODUCTION TO CHEMISTRY OF CARBONATES & BICARBONATES
https://en.wikipedia.org/wiki/Calciu...ate#Solubility

Too tired to read them right now, so will get back to that later.
Does it state anywhere the solubility of how many grams of bicarb vs carb can be dissolved in X amount of water?
Just from knowing that dissolved form would only be bicarbonates, wouldn't they have the same solubility?
Lol, I need to get some rest and research it.

Anthony


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post #11 of 13 (permalink) Old 05-10-2016, 03:34 PM
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You can make up a liquid KH booster. The amounts depend on what your'e using, the size of the tank, the dose size and the solubility of the chemical.

I have several listed in my Windows calculator if you don't want to do the calculations yourself.

Amount of each to raise one gallon of water 1 dKH

KHCO3 135.045657592 mg Solubility @ 20 C: 337g/l
K2CO3 93.212947875 mg Solubility @ 20 C: 1,110g/l
NaHCO3 21.761702144 mg Solubility @ 20 C: 96g/l

Example, Lets say you have a 10 gallon tank. You want to raise KH 2 dGH. Using a 1 liter bottle, a dose size of 30ml and K2CO3...

93.212947875 * 2 = 186.42589575 mg to raise 1 gallon 2 degrees

186.42589575 * 10 = 1,864.2589575 mg to raise 10 gallons 2 degrees

So one dose is 1,864.2589575 mg

1,000 ml / 30 ml = 33.333 doses in one liter

33.333 * 1,864.2589575 = 62,141 mg

Check solubility. 62.141 grams is 1,110g/l so your'e all set.

Add 62.141 grams to your 1 liter container and dose at 30 ml per 10 gallons to raise KH 2 dKH

btw, Solubility was obtained from a solubility table. No math involved


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post #12 of 13 (permalink) Old 05-11-2016, 08:10 PM
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There is no difference to dosing a freshwater tank vs a marine tank for KH maintenance, in a fundamental sense. You will certainly be dosing a lot less in most freshwater systems so that means use a less concentrated solution.

Ideally for a dosing pump, you want to be putting in small, daily amounts, matched to your consumption rate, to keep it as consistent as possible. So your solution concentration should keep this in mind.

Were you looking for someone to give you a favorable solution concentration and recipe?

Bump: There is no difference to dosing a freshwater tank vs a marine tank for KH maintenance, in a fundamental sense. You will certainly be dosing a lot less in most freshwater systems so that means use a less concentrated solution.

Ideally for a dosing pump, you want to be putting in small, daily amounts, matched to your consumption rate, to keep it as consistent as possible. So your solution concentration should keep this in mind.

Were you looking for someone to give you a favorable solution concentration and recipe?
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post #13 of 13 (permalink) Old 05-11-2016, 08:20 PM
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The difference between potassium carbonate and bicarbonate is the pH you end up with. With potassium carbonate it will Be higher.
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alkalinity, carbonate hardness or kh, dosing, freshwater aquarium, peristaltic pump

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