# baking soda KH question



## Ras (Nov 7, 2013)

If I am using RO water and adding seachem equilibrium for gh should I be adding calcium carbonate for KH instead of baking soda? I'm asking because I have snails and soon shrimp.


----------



## Argus (May 22, 2013)

Based on recommendations in other threads here, I'm using 



. It doesn't take much.


----------



## Audionut (Apr 24, 2015)

Calcium Carbonate is arguably the best source of carbonate (it doesn't add sodium or excess potassium), and it's buffering capacity is twice as good as bicarbonate. Dissolving it is the issue. Your best bet at dissolving it is by adding it to a high flow section of the tank (filter).

You cannot (initially) _simply_ say three grams of calcium carbonate added to the filter will give you this much KH. Since it is slow to dissolve, with the rate of dissolution being determined by the flow of water past the calcium carbonate, and the pH of the water. So if you go down this path, you'll need to add some to your filter, monitor your KH, and adjust the amount you have in the filter at any one time.



Argus said:


> It doesn't take much.


My math says 1.4 grams per 10 gallons will increase KH by 1.03 dKH. That same math also says K will increase by 14.4 ppm. IMHO, to many people jumping on the K is better for plants bandwagon, without considering how much K is being added.


----------



## Ras (Nov 7, 2013)

Audionut said:


> Calcium Carbonate is arguably the best source of carbonate (it doesn't add sodium or excess potassium), and it's buffering capacity is twice as good as bicarbonate. Dissolving it is the issue. Your best bet at dissolving it is by adding it to a high flow section of the tank (filter).
> 
> You cannot (initially) _simply_ say three grams of calcium carbonate added to the filter will give you this much KH. Since it is slow to dissolve, with the rate of dissolution being determined by the flow of water past the calcium carbonate, and the pH of the water. So if you go down this path, you'll need to add some to your filter, monitor your KH, and adjust the amount you have in the filter at any one time.
> 
> ...


they sell calcium carbonate powder at the health food store, seems like it would be pretty water soluble has anyone tried it?
potassium carbonate sounds like the next best thing, I dont mind a little extra potassium in my tank.


----------



## Diana (Jan 14, 2010)

Calcium carbonate, magnesium carbonate, coral sand, limestone sand or powder, and similar materials can raise both GH and KH. 
Some of these are just calcium and carbonate, and do not offer any magnesium. If you use one of these you may also want to add Epsom salt for magnesium. 

Plants use Ca and Mg in a ratio of about 4 parts Ca: 1 part Mg. The water does not have to have this exact ratio, but something in the neighborhood is good. 
There are ways to figure out how much to use. 
I would start with enough calcium carbonate to set the GH and KH about where you want it, then add enough Epsom salt to raise the GH by 1 degree. 

Ditto the other comments about allowing the calcium carbonate to fully dissolve- this may take time.

Bump:


----------



## Audionut (Apr 24, 2015)

Purchasing it at a health food store would be an extremely expensive way to purchase it. As Diana mentions, it's available in several forms that are likely to be far cheaper then powdered form from a health store.

Being powdered form will help solubility somewhat thanks to the increased surface area. However, the solubility of calcium carbonate is very poor, being only 0.013g / L @ 25c. So even with the increased solubility of fine form, it still isn't going to dissolve at any great rate. Also, being powdered form it's likely to clog things it shouldn't.

A better form would be shell grit or similar. In this manner you can add a handful or more, and it will slowly dissolve over time.

Since I completely missed the fact (sorry for dragging this thread down a path it probably didn't need to go) that you're looking to increase the KH of RO water, you are probably better off just using sodium or potassium bicarbonate (or a mixture of both), since these dissolve significantly easier. Calcium carbonate can be used, but you'll need to make your RO water acidic (perhaps with CO2), to dissolve the calcium carbonate at a rate that would make it feasible.


----------



## Ras (Nov 7, 2013)

I was planning to add enough kh to raise it to around 30 - 40 ppm then add enough seachem equilibrium to get the gh around 40-50 ppm during each water change. since the seachem has magnesium in it I assumed I wouldn't need to dose it. I just wasnt sure what would be best to use for kh since I have shelled animals, sounds like potassium carbonate is my best choice since it is soft water tank I dont want any extra salt that doesn't need to be there.

SO 
enough equilibrium to raise the RO water to 40 ppm gh (each water change)
enough potassium carbonate to raise kh to 30ppm (each water change)
add almond leaves.
am I missing anything to create healthy black water parameters?


----------



## Audionut (Apr 24, 2015)

Equilibrium contains potassium. 

Ditch the equilibrium and just add calcium and magnesium separately. Equilibrium uses calcium sulfate and magnesium sulfate. You'll be getting potassium from the potassium bicarbonate.


----------



## Oso Polar (Apr 22, 2015)

This thread reminds me of my own: http://www.plantedtank.net/forums/1...rameters/930817-minimum-gh-plants-shrimp.html

Unfortunately, it looks like not many people have experience with plants and shrimp in soft water. For now I plan to target dKH < 1, dGH = 2. Got potassium bicarbonate from nuts.com.


----------



## Diana (Jan 14, 2010)

> I was planning to add enough kh to raise it to around 30 - 40 ppm then add enough seachem equilibrium to get the gh around 40-50 ppm during each water change. since the seachem has magnesium in it I assumed I wouldn't need to dose it. I just wasnt sure what would be best to use for kh since I have shelled animals, sounds like potassium carbonate is my best choice since it is soft water tank I dont want any extra salt that doesn't need to be there.
> 
> SO
> enough equilibrium to raise the RO water to 40 ppm gh (each water change)
> ...


Correct- Equilibrium has both Ca and Mg. No need to dose more of either. 
Use potassium bicarbonate.

--------------------------------------------------------------------------------------------

Cheapest and finest milled source of calcium carbonate is Oyster Flour. 
It is available in the local feed store as a horse stall deodorizer, and people use it for the surface of bocce courts. 
50 lb bag is $11.99 
I have no idea if it is pure enough to use in aquariums. I did collect a cup or so from the last bocce court we built, and will test it some time this winter. Possible contaminants:
Salt from the ocean
Meat from the oysters
Other?
Since it is used in an outdoor setting, exposed to rain, I really doubt it is going to dissolve very well.


----------



## Audionut (Apr 24, 2015)

Be careful targeting very low amounts of GH and KH. The low KH means very little buffering capacity against pH swings. Reasonably low levels of chemistry changes can easily convert the little bicarbonate available to acid, lowering pH significantly and causing all sorts of problems.

In other words, any minor accidents, or circumstances not accounted for, have a greater chance of causing very large issues.

For what ever it's worth, my tank is at TDS 150ppm, 3.75 dGH and 3.25 dKH. With N (20ppm), P (5ppm) and K (20ppm) or thereabouts.

dGH results are measurements of (mainly) calcium and magnesium, as a CaCO3 (calcium carbonate) equivalent. So if your GH is entirely calcium, and the dGH reading is 2dGH, then the concentration of calcium in the water is _only_ 14.3ppm, not 35.7ppm as might be implied by converting dGH to ppm. If the GH was entirely magnesium, then the concentration of magnesium in the water would _only_ be 8.7ppm.

This is because the molar mass of calcium is 2.5 times lighter then calcium carbonate, with magnesium having a molar mass 4.12 times lighter.


----------



## Ras (Nov 7, 2013)

Audionut said:


> Be careful targeting very low amounts of GH and KH. The low KH means very little buffering capacity against pH swings. Reasonably low levels of chemistry changes can easily convert the little bicarbonate available to acid, lowering pH significantly and causing all sorts of problems.
> 
> In other words, any minor accidents, or circumstances not accounted for, have a greater chance of causing very large issues.
> 
> ...


there shouldn't be any swings, it should stay mainly acidic since I replace the almond leaves in my tank every 2 weeks or so. the water stays a dark brown color all year. not sure how fast old snail shells leach into the water but that will be the only other source of kh in the tank, and I use an air pump rather than co2 so that shouldnt effect the ph. and I can remove most of the shells if I notice the ph or kh start to rise


Diana said:


> Correct- Equilibrium has both Ca and Mg. No need to dose more of either.
> Use potassium bicarbonate.


ah i see, BIcarbonate, not carbonate. and this would be at a natural food store or something? and is there an amount to start at when I test to find out how much I need per WC? "1gram per 5gallons for 10ppm kh" or something along those lines, so I have a starting point.


----------



## Audionut (Apr 24, 2015)

Ras said:


> there shouldn't be any swings, it should stay mainly acidic since I replace the almond leaves in my tank every 2 weeks or so. the water stays a dark brown color all year. not sure how fast old snail shells leach into the water but that will be the only other source of kh in the tank, and I use an air pump rather than co2 so that shouldnt effect the ph. and I can remove most of the shells if I notice the ph or kh start to rise


Dependent on the pH of the water, the air pump is likely to increase pH.

Consider this relationship between CO2 and carbonic acid.










Notice how the arrows go both ways. So increasing CO2 increases carbonic acid, and increasing carbonic acid increases CO2.

As pH lowers, the water contains increased H+ ions, which bond with bicarbonate and carbonate to form carbonic acid. This carbonic acid will maintain an equilibrium with CO2 + H2O. More carbonic acid (lower pH), more CO2.

However, since water will want to maintain an equilibrium with the surrounding atmosphere (Henry's law), any increase in CO2 molecules in the water will escape into the surrounding atmosphere. An air pump will increase surface agitation, increasing the rate at which the water and air reaches equilibrium. ie: It will drive off (any excess) CO2 (above equilibrium with the atmosphere) faster, and since there is less CO2 in the water (because the air pump is pushing the excess CO2 into the atmosphere), some of that carbonic acid will convert back to bicarbonate, increasing pH.

H+ ions (acid) from the almond leaves are a form of total alkalinty. However it should be noted that H+ ions _already in the water_ do not increase total alkalinity. H+ ions already in the water are easily used in the process of converting carbonic acid to bicarbonate to carbonate, and vice-versa.

The _addition_ of H+ ions to the water will however buffer the water. The pH at which this occurs will be dependent on the amount of bicarbonate and carbonate in the water. With a source of bicarbonate and carbonate in the water, the H+ ions will react with these carbonates to form carbonic acid, which will maintain equilibrium as I described above.

However, if the bicarbonate/carbonate source depletes, the pH can drop rapidly to a very low value, since there's no more carbonate sources to maintain equilibrium. ie: The pH will buffer at a very low value.

Old snail shells are caclium carbonate (CaCO3). So they provide a carbonate source to the aquarium, and since they are a carbonate, and not a bicarbonate, they provide the strongest form of total alkalinity thanks to the carbonate ability to accept two H+ ions, compared to bicarbonates ability to _only_ accept one H+ ion. The rate at which the shells dissolve into the water is determined by how acidic the water is. Any H+ ions (acid) added to the water will bond with carbonate in the shells. More H+ ions added, more bonding, faster dissolution.

Hopefully that all made sense. If it didn't, or otherwise, my recommendation would be to start with a higher carbonate source in the water then might otherwise be needed. This *will* provide protection against any errors, mistakes, or circumstances that were not considered. ie: If something goes wrong, you have a significantly better chance of fixing the problem before equilibrium of the chemical species is lost, resulting in the carbonate equilibrium shifting to the left, crashing pH.

The pH will stabilize at some value above your desired pH. With monitoring of the carbonate hardness (KH), you can then begin to remove some of the carbonate source from the water, through the removal of snail shells (or other carbonate source) from the water , or the reduction of (sodium/potassium) bicarbonate dosing. This reduction in the carbonate source will lower the pH. It should be noted that this is a balancing act between the amount of acid added. Adding more almond leaves will dissolve the carbonate sources faster.

You did imply these are the steps you would take, by removing shells if KH increases. A little chemistry theory doesn't hurt though..........right? :icon_roll


----------



## Diana (Jan 14, 2010)

Potassium bicarbonate:
1/8 tsp in 1 gallon of water will raise the KH by 6 degrees. (per my test, API KH test)

Sodium bicarbonate:
1 teaspoon in 30 gallons of water will raise the KH by 2 degrees. (per my test, API KH test, and test strips, 29 gallon tank with a Fluval 204 canister, so the '30 gallons' is sort of rounded. But I have also dosed tanks from 10 gallons to 50 gallons with this recipe and it is accurate enough for hobby level test kits)

Both of these recipes respond to simple math. here are some other ways of stating the same thing:
Potassium bicarbonate:
1/8 tsp in 1 gallon of water will raise the KH by 6 degrees.
1/8 tsp....2 gallons.......................................3 dKH.
1/8 tsp....4 gallons.......................................1.5 dKH

Sodium bicarbonate:
1 teaspoon in 30 gallons of water will raise the KH by 2 degrees. 
1 tsp in 15 gallons..........................................4 dKH
1/4 tsp in 15 gallons......................................1 dKH
1/8 tsp in 1.5 gallons ....................................5 dKH

I would run a known volume of water into a bucket and add a small dose of either of these. Stir well. Test after a few minutes to an hour. Let it stand overnight and test again. 
This will show you how fast the materials dissolve, if any lingers to dissolve more slowly, and what effect it has on your water. Confirm or alter the recipe for your tank. 
----------------------------------------------------------------------------------

If you put any of the following materials in a bag (nylon stocking works well) in the filter it will have a reasonably fast effect, and is easily removed if it is going too far. 

Oyster shell grit, sold for caged birds. The size for Budgies is coarse sand, pretty good for the tank. Larger pieces are available for chickens, but these dissolve more slowly. 

Coral sand, available in aquarium stores. 

Aragonite substrate, available in aquarium stores. 

Limestone sand. (Not sure where this is available- make some calls)
Limestone gravel. Try a rock yard. Get whatever material bubbles the strongest when you drip some vinegar onto it. 

Dolomite sand (high in magnesium) sold for certain landscape/masonry projects. You will have to figure out a dose for this, but it reacts FAST and STRONG. I put just a pinch in a glass of tap water (pH in the upper 7s, GH and KH around 4-5 degrees) and within 2 hours the KH and GH were rising. If you decide you want to use this material you might dissolve some first in a glass of water, then just pour a small amount of the water into the tank. I dusted a trace of this under some substrate that tends to remove the KH from the water, and have had no problems with the water in the tank maintaining the right GH and KH. (It is actually going up a bit- this is OK, I keep livebeareres in this tank)


----------



## Ras (Nov 7, 2013)

thank you for the info! I was hoping to use something that was almost instantly water soluble so kh wont slowly rise between water changes. does potassium bicarbonate take more than a day to dissolve fully? the less fluctuations during wc the better and so I dont have to do more testing than I need to


----------



## Hoppy (Dec 24, 2005)

"Buffer Definition:
A buffer is a solution containing either a weak acid and its salt or a weak base and its salt, which is resistant to changes in pH." from Buffer Definition - Chemistry Glossary

The buffer we get with KH consists of a weak acid, H2CO3 (carbonic acid) and (X)HCO3, a salt that contains the conjugate base for carbonic acid, HCO3-. That buffer maintains the pH of the water at the value that corresponds to the KH of the water and the amount of dissolved CO2 in the water. It buffers against weak acids like tannic acid from sources in the water. *It does not buffer against addition of more CO2 or more KH.*

Just to clarify the chemistry a bit.


----------



## Argus (May 22, 2013)

Ras said:


> thank you for the info! I was hoping to use something that was almost instantly water soluble so kh wont slowly rise between water changes. does potassium bicarbonate take more than a day to dissolve fully? the less fluctuations during wc the better and so I dont have to do more testing than I need to


Potassium bicarbonate dissolves very quickly.


----------



## Ras (Nov 7, 2013)

awesome. taking everything into account potassium bicarbonate sounds perfect for what I need, thanks again everyone


----------



## Diana (Jan 14, 2010)

Ditto- it does dissolve fast. I was simply being cautious in suggesting that you monitor a test batch to see if it was going to do something unusual. 

The other materials that I listed in post 14, under the line, are slow, good additions to the filter if there is something in the tank that is slowly removing any of these minerals- For example, some substrates remove carbonates from the water.


----------



## DaveFish (Oct 7, 2011)

Potassium Bicarbonate buffer:

Make a 300g per 1 liter solution.

dose 30ml per 40 US gallons / 151 liters to raise KH by 2 degrees (dKH) = 36ppm

Recommended levels are between 2.8-5.6 dKH or 50-100ppm

This also raises potassium by 23mg per liter or 23ppm

*apply this dosing volume to the TRUE amount of water taken out and put back into the tank each week, and not the total tank volume! It is preferred to use RO/DI water. For unbuffered water or in the absence of CO2 injection, use 1/4 to 1/2 dose to avoid impacting pH. I run my tank at 3KH, 6-7GH, with a 6.6 pH.
And these are all really guidelines because each tank is different and we are not always consistent. So, always test the KH of your water when first getting down a routine. After a routine is established you can check every month or so to make sure you are still on track. Sometimes your KH can accumulate if you did a tap water evaporation refill, or dosed too much one week, so always monitor your KH, but truly in this situation it is alkalinity considering we are not using calcium bicarbonate or magnesium bicarbonate.

I hope this helps.

You can get potassium bicarbonate off of Amazon for super cheap, and it will last you a few years. They use it in wine production.


----------



## Audionut (Apr 24, 2015)

Hoppy said:


> It does not buffer against addition of more CO2 or more KH.


Correct. Because both of these shift the equilibrium of the carbonate buffer.


----------



## HiepSTA (Aug 23, 2011)




----------

