Calcium chloride to lower PH

[Cdsdave]

Hi all. I used baking soda to raise my KH but now my PH is at 9.0. When I first did the baking soda my PH went up to the 8.4-8.6 range from 8.0. I've read where calcium chloride will lower the PH to 8.3 if baking soda has been used to raise the KH. My questions are what and where do I get calcium chloride( is it a salt?) and how much to use per 1000 gallons?

 

[crsublette]

Around 8.3~8.5. There is approximately a +/- .2 variance, although most definitely below 8.7, here dependent on your pond water's chemistry.

Calcium chloride from your local hardware store. Be sure it is 98~100% pure calcium chloride. No additives. 1 pound (or 16 ounces) per 1,000 gallons.

It is a salt due to the presence of chlorides, but this is not the same type of salt as described by sodium. Chlorides and chlorine are not the same. Chloride is one essential nutrient in organic life and especially plant life. Chlorides increases plant's hardiness to extreme environments, but too much chloride can result to plant phytoxicity concerns. However, in our context in an outdoor pond, with many plants, algaes, and complete water changes above 3% per week, the amount of chloride accumulated from using calcium chloride will never be a concern. "Complete" water changes occurs when old water is remove when new water is added. Only adding water due to evaporation, and never removing an equal amount of old water, will allow the chlorides to accumulate, but, if you enough plants, then this will never be a concern. Chloride also helps your fish improve their defenses to combat nitrite toxicity.

 

[HARO]

Cheapest source is packaged as a salt melter, but you can only get it in winter. This time of year you can get it as a dust control for unpaved parking lots or a concrete additive to speed up setting. The stuff I got here is produced by Occidental Chemical Corporation of Dallas, Texas, and labelled 83-87% pure Dowflakextra calcium chloride. A 44 lb. bag costs about $15. here. Information on its use as a Ph stabilizer can be found here under many of Waterbug's posts, or on his website. Try a building supply place or a farmers supply.
John

 

[crsublette]

Yep, the hyperlink I reference to is one version of an ice and snow melter (not salt melter). It is an extremely common and popular product used in the entire hobby, referenced on any serious pond hobbyist forum, to reduce the pH.


Now... In regards to your reading of a pH of 9.0, I think there needs to be clarification.

The liquid regeant pH test kits have at the very least a +/- .2 variance in regards to their accuracy. The test strip's accuracy is even worse than this.

So, if you are quite positive that your pH is 9.0 or higher due to the addition of baking soda, than increasing the calcium concentrations will reduce the pH level.

 

[crsublette]

If the pH increases to 9.0 or higher, then I would definitly dose the water with some calcium chloride.


I completely forgot to mention one very important instruction.

Do not add calcium chloride (CaCl) right after or right before using baking soda. Wait at least 12~24 hours between dosing the water, before or after, with baking soda (NaHCO3). Eventhough these two products are fast dissolvents, it still takes time for the products to equilibriate through out the water. If you do not wait long enough, then the carbonates (CO32-), that is created by the sudden increase in bicarbonates (HCO3), will very quick combine with the calcium (Ca++), that is released from calcium chloride, to create a pure calcium carbonate product (CaCO3), creating a white residual in the water, that will not readily dissolve in the water unless the pH of the water lowers, and the residual would be sodium chloride (NaCl), that is table salt.

Also, since dissolving calcium chloride will create a significant amount of heat, then dissolve this product in a bucket prior to pouring it into the pond.

 

[Cdsdave]

I tested the PH in the evening 7:30 and its registering 9 on the WRPH tester and this color (see pic) onthe HRPH tester. This color doesn't really match the colors on the ref card too closely. When I did these tests during the morning(6:30) they registered 8.0 WRPH and 8.2 HRPH. My KH is 7 GH is 3. I have a bag of crushed oyster shells (approx 5 lb) in the skimmer. Should I add more baking soda to raise KH? Should I use the rock salt to lower the PH? Do both? What about raising the GH with rock salt and Epsom salts? Thanks for everyone's input!!

 

[Cdsdave]

Okay so what I have is sodium chloride not calcium chloride so I WON'T be putting that in the pond . I will have to check the local hardware stores and see if they have any left overs from winter.

 

[crsublette]

Yeah, the WRPH tester is really more used to determine if you should use the LRPH or the HRPH since these two testers will give you a more accurate reading at a particular range.

For your KH and GH questions, check out the thread, proper KH and GH levels.

Rock salt, that is sodium chloride, will not help to lower your pH.


For folk not good with acronyms:
WRPH - Wide range pH
LRPH - low range pH
HRPH - high range pH

 

[Cdsdave]

Should I concentrate on the KH and let the PH be for now? Like I said in an earlier post, the PH has fluctuated from around 8.0 in the morning to 9.0 n the evening. Should I be concerned about a 1 degree swing? I did find some calcium chloride ( safe step) in case I need to use it. Charles you said 1 lb for every 1000 gallons? How often do I dose or is it a 1 time deal? What will that drop the PH To? I've read the PH KH GH link several times before. It's very informative. He said it was best to adjust the KH and not try to adjust the PH directly. What's your opinion. Thanks for your help!

 

[crsublette]

GH (calcium specifically) only stabilizes the high end of the pH fluctuations, that is any swing above around 8.3~8.5 pH.

KH only stabilizes the low end of the pH fluctuations, that is any swing below around 8.3~8.5 pH.

What is a healthy pH swing? It all depends on who you ask. Big aquaculture fish farms, involving hardy fish species such as carp, and some planted tank aquarists experience quite large 2 degree swings and never report any fish loss due to a 2 point pH swing within 24 hours, but this type of pH swing should not be considered healthy at all since it definitely does stress the fish's immune system. Some hobbyists will say any pH swing bigger than .2 within 24 hours is too much. Personally, I think if the pH swing within 24 hours is around .2 ~ .4 is fine, since this is what I experience in my system. If it is closer to .4 pH swing end of it, then I would take some serious action to increase the KH or calcium concentration until I am satisfied with the swing. Although, keep in mind of the accuracy of your test kit. I use a pH continuous monitor with electronic diodes, a bit expensive and a favorite toy of mine, to monitor my pH within an accuracy of +/- .01.

If you are using a liquid pH test kit, this testing methodology has an accuracy of +/- .2. So, if you are using a liquid pH test kit, then I would agree with the other hobbyists that say any pH swing bigger than .2 within 24 hours is too much.

For calcium chloride, it is 1 pound every 1000 gallons. The number of doses will depend on your water chemistry. So, do the "dose and wait" methodology. Dose the water once, wait 24 hours, and see if the calcium has stabilized the high end of the pH range, as described as any swing above around 8.3~8.5 pH. If the calcium pushes the pH no lower, than stop the dosing.

Document it so next time you know how much to dose.

Very important to document everything you're doing since it is good data to keep in the library as a reference guide for future dosages.

Your last question involves a bit more detailed explanation. So, keeping it in next post here, give me a moment.

 

[crsublette]

He said it was best to adjust the KH and not try to adjust the PH directly. What's your opinion.

Short answer....

Correct, it is best to adjust KH when you are trying to adjust the pH to be lower since the KH is what controls the low end of the pH range and prevent the pH from changing lower.

Here is my attempt at explaining on how to stabilise a pH at 7.0 for a freshwater outdoor pond.

Grr, I can't find the thread I wanted to, but to quickly tell ya... Oyster shells (calcium carbonate) works better when the pH is below 8.3~8.5 since it functions more as a KH stabilizer rather than a calcium stabilizer eventhough it does release some calcium.


Long answer....

A layman version of the Henderson-Hasselbalch equation for the pH formula is... pH = pKa + log([HCO3-]/[H2CO3])... H2CO3 is carbonic acid, that is created when carbon dioxide (CO2) dissolves into water (H2O). Carbonic acid is considered to be the weak acid. HCO3- is the inorganic carbon, bicarbonate, that is found in baking soda, which is sodium bicarbonate (NaHCO3). Bicarbonate is considered to be a form of salt that reacts with carbonic acid. The relationship between a weak acid and its salt is what creates the buffer, which then determines the pH. There are two salts that react with carbonic acid. One salt is bicarbonate (HCO3-) and the other salt is carbonate (CO32-). This particular buffer system is called a carbonate buffer whenever these two salts and carbonic acid are predominant in the pond water. pKa is the coefficient of the hydrogen cation (H+) present in the salt. Since there is only one hydrogen cation present between the two salts, then this indicates there is only buffer range for the bicarbonate/carbonate buffer range, which is around 8.3~11.2. As nature creates hydroxides (OH-), then carbonates (CO32-) are created and this increased carbonate concentration raised the pH above 8.3. When the water is more closely to complete bicarbonate concentration, then the water's pH is around 8.3~8.5. When the water is more closely to complete carbonate concentration, then the water's pH is around 10.8 ~ 11.2.

Do not confuse sodium (Na++) by calling this a salt. In stoichemistry, sodium acts as a type of electrolyte, in regards to these buffer systems. Sodium is often used since its electochemical bond is very easy to break in water to release constiuent component, such as bicarbonate in baking soda (that is sodium bicarbonate).

There is also an equilibrium dance that occurs with carbonic acid (H2CO3), bicarbonate (HC03-), carbonate (CO32-), and carbon dioxide (CO2-). To better understand this pattern, then google "freshwater carbonate speciation diaphragm", which is a Bjerrum plot. Many environmental variables change this diaphragm so the ones you google will not necessarily apply to your pond water, but it is close enough to give you an idea of the equilibrium dance that is occuring.


So, after that nasty technical explanation and leaving out some other details, this partially explains how KH and pH are related. When KH changes, the equilibrium dance allows the pH to change. KH is simply a better control variable that applies to the low end of the pH range when wanting to lower the pH rather than using the pH test kits. When you are changing the pH, you want to look at the most accurate proactive control variables that are available.

pH tests tell you how the water is reacting to the stabilizer products. Stabilizer products such as calcium chloride, baking soda, calcium carbonate, etc. This is why you are being reactive when testing pH and proactive when testing for the KH or GH (calcium).

Although GH test kits also test for a presence of calcium, keep in mind GH tests are testing for many other divalent minerals, which are any mineral with two positive charges, that have zero impact on stabilizing pH and this same definition can only be loosely applied to KH. Divalent minerals are sodium (Na++), calcium (Ca++), iron (Fe++), magnesium (Mg++), manganese (Mn++), and many other minerals. GH test kits is not a direct calcium test kit. You can get a calcium test kit, which are used by coral reef keepers, but they are significantly more expensive.

You can document the GH test kit number to indicate whenever your calcium concentrations start to drop, but, if you are using Koi Clay or plant medium or other products in the water that add to the minerals, then the GH test kit is not a reliable way to indirectly test for calcium.

So, a cheaper route and more accurate route is to indirectly test for calcium by monitoring reactive control variables, that is the pH. When pH reaches 9.0 or higher, then this means your calcium concentrations is starting to become too low to stabilize the high end pH range. The calcium concentrations required is dependent on the pond's water chemistry and other contaminants present in the pond.

Alkalinity is simply any buffer element, including borate, phosphate, bicarbonate, and many other buffer combinations, that helps water resist a decrease in pH change contributed by an acid that releases free hydrogen cations (H+). KH tests this type of pH change tolerance, when decreased, in the water's alkalinity. KH test kit is not a direct test for bicarbonates, such as baking soda, but there is zero practical test a hobbyist can do to test for the true bicarbonate concentration. KH is an acid titration plus indicator solution test. The reagant in the KH test kit is actually a weak acid, custom made by the manufacturer, with a set pH in the low 5s, around 5.0~5.4 pH. A solution is acidic due to the extra hydrogen cations (H+). Whenever an acid reacts with water, the extra hydrogen cations react with the alkalinity buffers, essentially "burning" away the alkalinity, that are present until the water's pH reaches the pH of the reagant solution. Bicarbonate is known to be present in the pH range of 5.0~8.5 and 8.3~8.5 is its baseline pH. So, when the KH test kit vial solution changes colors, then this indicates the pH of the vial solution is around lowish 5.0s, which means there is very little measureable bicarbonate present. This is why we are assuming the KH test kit is a test for bicarbonate (HCO3-). This is how the API KH test kit functions. So, if it took 4 drops of reagent to merely just noticeably change colors in the vial, then this means all of the alkalinity has been "burnt" off and then we multiply 17.848 by 4 drops to get 71ppm or 71mg/L of alkalinity. There is a more precise definition for the term KH so to use KH in reference to alkalinity is not entirely correct, but it is just the common marketing nomenclature used nowadays since it is faster/shorter to type.

As far as I am aware, the only way to indirectly test for carbonate (CO32-) is to use a HACH alkalinity reagant titration test kit using a phenolphthalein acid regeant, which has a pH of 8.3, and I am told this type of test is more prominent in coral reef aquariums, although not for sure why except maybe to test for the calcium hardness. When the vial's water solution reaches a 8.3 pH, then this means there is very little measureable carbonate present.

Carbonate (CO32-) has a strong electrochemical affinity to connect to Calcium (Ca++). So, when free soluble calcium is present, then carbonate and calcium precipitates by forming an insoluble product called calcium carbonate (CaCO3). As the water becomes more acidic, then the free hydrogen cations (H+) breaks this electrochemical bond of calcium carbonate (CaCO3) causing it to dissolve so to created bicarbonate (HCO3-) and free soluble calcium (Ca++), at different concentrations depending on the molar mass of the acid.

Not all compounds are instantly consumed. There will always be a presence of calcium, bicarbonate, carbonate, carbon dioxide, and carbonic acid present in the water. So, even though you might have 20 mg/L of free soluble Calcium in the water, this does not necessarily mean this is the amount that is needed to neutralize the present carbonate. This is only one reason why some ponds might require more calcium than other ponds.

There are many other equilibrias involved as well such as ammonia and phosphates, but this is the general jest of it.


It is all just basic pond water chemistry. It's not rocket science. :cheerful: :claphands:


So, you kind of see how everything comes in full circle... that is if I did not mangle the explanation too much. I am relatively young to this as well, but I find the technical details relaxing and enjoyable. Give a yell if ya need any clarification or question.

 

[Cdsdave]

THANKS for the detailed explanation. I am going to read it through closely and take the steps needed to stabilize the PH. I will let you know how it's going and appreciate your help. Take care and will write soon!!

 

[Cdsdave]

Okay, I did 2 doses of calcium chloride over 2 days and tested the PH. The last 2 days the readings in the morning have been 8.2 and in the evening 8.4 approx. I'm happy with these readings!! Tomorrow I test all my levels and will see what my KH is reading. If I end up adding more baking soda to raise the KH(it's been testing 7)would that throw off the PH again?

 

[crsublette]

Very good man. :beerchug: Can't deny the chemistry. It works everytime.


KH raise through Baking soda stabilizes the pH. It does not throw it off. It will increase it up until around 8.3~8.5, within a +/-.2 variance of this, at around 9 dKH (or 9 drops, that is 160ppm KH). The pH will remain around 8.3~8.5 anything above around 9 dKH, as long as your calcium concentration is good. Event at 22 dKH, the pH will still be around 8.3~8.5, as long as your calcium concentration is good.


You mainly just want a stable and constant pH to be healthy for your fish and biofilter.


If it is still stable and healthy with just 7 degrees (or drops) of KH, then this is good. Although, if it rains quite a bit, then I would raise it higher to at least around 10~11 dKH (drops).

 

[Cdsdave]

I just tested my levels and my KH is down to 4 from 7? Could the calcium chloride have brought it down? This morning my WRPH was 8.2 now at 3:45 it's up past the 8.4 mark closer to the 8.8 range (similar to the earlier photo I submitted). We did get a brief downpour last night. I am going to add 4 oz. of baking soda to raise the KH up. Another interesting thing is my GH has gone from 3 to 16!!! Good I suppose but how did that happen? The calcium? I will test PH again after dinner and see if today was a fluke.