How to use Kalkwasser effectively?

[Splee]

First off, what causes Kalkwasser to raise alkalinity? Since it doesn't have carbonate in it, what happens to the hydroxide that causes alkalinity to increase? Is it something that will continue to accumulate if my corals can't consume it all?
Second, I'm attempting to combat my low pH (lows of 7.7, high of 7.95) but I'm only seeing my pH rise to a new peak of 8.07. Do I need to simply dose the kalkwasser more quickly? Im currently using two BRS 1.1ml dosers that run 24/7 but I'm just not seeing the pH bump I was hoping for. What is the longevity of the pH increase? If I have to dose more quickly, will I just see huge swings up and down?
Thanks
Edit: My kalkwasser is being dosed out of a gallon jug, 2 tsp per gallon with settlement at the bottom

 

[HuduVudu]

First off, what causes Kalkwasser to raise alkalinity?

Kalkwasser is calcium hydroxide. This is Ca+2 and OH-. This is simple a calcium ion and a hydroxl ion (base). Alkalinity is the ability of a solution to absorb acid (H+) without changing the pH. Kalkwasser uses the carbonate from carbonic acid (dissolved CO2) to add calcium AND carbonate to the solution.

Since it doesn't have carbonate in it, what happens to the hydroxide that causes alkalinity to increase?

The hydroxl ion of the Kalkwasser combines with the hydrogen ion from the carbonic acid to create water. OH- + H+ --> H2O

Is it something that will continue to accumulate if my corals can't consume it all?

Carbonic acid is always present in water assuming that there is gaseous CO2 available to the air water surface. The CO2 dissolves in the water and some portion of this dissolved CO2 converst to carbonic acid H+ + CO3-

Second, I'm attempting to combat my low pH (lows of 7.7, high of 7.95) but I'm only seeing my pH rise to a new peak of 8.07. Do I need to simply dose the kalkwasser more quickly?

The problem with this thinking is that you are not understanding the source of acid that is depressing your pH. There are multitude of acid sources in salt water aquariums. The biggest sources are from gaseous CO2 over the tank, aerobic breakdown and respiration.

So you need to know what the CO2 of the room is. You need to know understand how much you are feeding and it's effect and you need to evaluate the fish load of your tank.

 

[Arego]

^ That.. and stuff.

 

[Randy Holmes-Farley]

First off, what causes Kalkwasser to raise alkalinity? Since it doesn't have carbonate in it, what happens to the hydroxide that causes alkalinity to increase? Is it something that will continue to accumulate if my corals can't consume it all?
Second, I'm attempting to combat my low pH (lows of 7.7, high of 7.95) but I'm only seeing my pH rise to a new peak of 8.07. Do I need to simply dose the kalkwasser more quickly? Im currently using two BRS 1.1ml dosers that run 24/7 but I'm just not seeing the pH bump I was hoping for. What is the longevity of the pH increase? If I have to dose more quickly, will I just see huge swings up and down?
Thanks
Edit: My kalkwasser is being dosed out of a gallon jug, 2 tsp per gallon with settlement at the bottom

Hydroxide itself is a perfectly fine alkalinity supplier. 0.1 mM NaOH has 0.1 meq/L of alkalinity even when measured directly with nothing else happening.

But when added to seawater, this happens:

What Your Grandmother Never Told You About Lime by Randy Holmes-Farley - Reefkeeping.com

What Is Limewater?

Aquarists have used limewater very successfully for a number of years, and it is the system that I use in my aquarium. It is comprised of an aqueous solution of calcium and hydroxide ions that can be made by dissolving either quicklime or lime in fresh water. Note that the water must be freshwater. Combining lime with seawater will result in a mess of precipitated magnesium and calcium carbonates and hydroxides.

The only inherent difference between calcium oxide and calcium hydroxide is that adding a molecule of water to quicklime produces lime, and that a great quantity of heat can be generated when that happens.

3. CaO + H2O --> Ca(OH)2

Quicklime + Water --> Lime

Consequently, dissolving quicklime can make water quite warm, especially if an excess of solids is added. Some aquarists have damaged equipment by adding a large amount of quicklime to a small amount of water in a plastic reactor. The heat released can easily boil the water, and some plastic devices may not be able to withstand that hot, corrosive mixture.

The calcium ions in the solution obviously supply calcium to the aquarium, and the hydroxide ions supply alkalinity. Hydroxide itself provides alkalinity (both by definition and as measured with an alkalinity test), but corals consume alkalinity as bicarbonate, not hydroxide. Fortunately, when limewater is used in a reef aquarium, it quickly combines with atmospheric and dissolved carbon dioxide and bicarbonate to form bicarbonate and carbonate:

4. OH- + CO2 --> HCO3-

5. OH- + HCO3- --> CO3-- + H2O

In an aquarium with an acceptable pH, there is no concern that the alkalinity provided by limewater is any different from any other carbonate alkalinity supplement. The hydroxide immediately disappears into the bicarbonate/carbonate system. In other words, the amount of hydroxide present in aquarium water is really a function of only pH (regardless of what has been added), and at any pH below 9, it is an insignificant factor in alkalinity tests (much less than 0.1 meq/L). Consequently, the fact that alkalinity is initially supplied as hydroxide is not to be viewed as problematic, except as it impacts pH (see below).

Limewater that is saturated with calcium hydroxide has a pH of 12.54 at 25ºC. It is actually recognized as a secondary pH standard. The pH is substantially higher at lower temperature (12.627 at 20ºC and 13.00 at 10ºC), and lower at higher temperature (12.289 at 30ºC; 11.984 at 40ºC). Saturated limewater has a conductivity of about 10.3 mS/cm at 25ºC, and contains about 808 ppm of calcium and 40.8 meq/l of alkalinity. Slightly more calcium and alkalinity dissolve at lower temperatures, and less at higher temperatures. Of interest to chemists, a large fraction of the calcium in saturated limewater is present as the ion CaOH+, with the remainder being Ca++. The CaOH+ will instantly dissociate into Ca++ and OH- upon its addition to aquarium water.

 

[Splee]

Kalkwasser is calcium hydroxide. This is Ca+2 and OH-. This is simple a calcium ion and a hydroxl ion (base). Alkalinity is the ability of a solution to absorb acid (H+) without changing the pH. Kalkwasser uses the carbonate from carbonic acid (dissolved CO2) to add calcium AND carbonate to the solution.


The hydroxl ion of the Kalkwasser combines with the hydrogen ion from the carbonic acid to create water. OH- + H+ --> H2O


Carbonic acid is always present in water assuming that there is gaseous CO2 available to the air water surface. The CO2 dissolves in the water and some portion of this dissolved CO2 converst to carbonic acid H+ + CO3-


The problem with this thinking is that you are not understanding the source of acid that is depressing your pH. There are multitude of acid sources in salt water aquariums. The biggest sources are from gaseous CO2 over the tank, aerobic breakdown and respiration.

So you need to know what the CO2 of the room is. You need to know understand how much you are feeding and it's effect and you need to evaluate the fish load of your tank.

Thanks for the response. So if I'm understand this correct, adding kalkwasser is just nullifying the current carbonic acid, but if the room itself is saturated with C02, it will continuously replenish the carbonic acid as long as their is ample gas exchange?
Would it make sense to run the skimmer at night to promote gas exchange while there is no photosynthesis and turn it off during the day to attempt to trap oxygen in the tank during the day and expel excess C02 at night?

 

[HuduVudu]

So if I'm understand this correct, adding kalkwasser is just nullifying the current carbonic acid, but if the room itself is saturated with C02, it will continuously replenish the carbonic acid as long as their is ample gas exchange?

Yes.

Would it make sense to run the skimmer at night to promote gas exchange while there is no photosynthesis and turn it off during the day to attempt to trap oxygen in the tank during the day and expel excess C02 at night?

If you have too much room CO2 then there will always be large amounts of carbonic acid in your tank. If your skimmer is connected to the outside changes the equation because now you are dealing with a relatively known CO2 amount. Be warned this isn't the ONLY source of acid in your tank. As I mentioned there are others and you need to determine one by one which is contributing and then work to eliminate it's contribution the best that you can.

Knowing your room CO2 is a VERY good place to start in understanding pH issues.

 

[Splee]

Hydroxide itself is a perfectly fine alkalinity supplier. 0.1 mM NaOH has 0.1 meq/L of alkalinity even when measured directly with nothing else happening.

But when added to seawater, this happens:

What Your Grandmother Never Told You About Lime by Randy Holmes-Farley - Reefkeeping.com

What Is Limewater?

Aquarists have used limewater very successfully for a number of years, and it is the system that I use in my aquarium. It is comprised of an aqueous solution of calcium and hydroxide ions that can be made by dissolving either quicklime or lime in fresh water. Note that the water must be freshwater. Combining lime with seawater will result in a mess of precipitated magnesium and calcium carbonates and hydroxides.

The only inherent difference between calcium oxide and calcium hydroxide is that adding a molecule of water to quicklime produces lime, and that a great quantity of heat can be generated when that happens.

3. CaO + H2O --> Ca(OH)2

Quicklime + Water --> Lime

Consequently, dissolving quicklime can make water quite warm, especially if an excess of solids is added. Some aquarists have damaged equipment by adding a large amount of quicklime to a small amount of water in a plastic reactor. The heat released can easily boil the water, and some plastic devices may not be able to withstand that hot, corrosive mixture.

The calcium ions in the solution obviously supply calcium to the aquarium, and the hydroxide ions supply alkalinity. Hydroxide itself provides alkalinity (both by definition and as measured with an alkalinity test), but corals consume alkalinity as bicarbonate, not hydroxide. Fortunately, when limewater is used in a reef aquarium, it quickly combines with atmospheric and dissolved carbon dioxide and bicarbonate to form bicarbonate and carbonate:

4. OH- + CO2 --> HCO3-

5. OH- + HCO3- --> CO3-- + H2O

In an aquarium with an acceptable pH, there is no concern that the alkalinity provided by limewater is any different from any other carbonate alkalinity supplement. The hydroxide immediately disappears into the bicarbonate/carbonate system. In other words, the amount of hydroxide present in aquarium water is really a function of only pH (regardless of what has been added), and at any pH below 9, it is an insignificant factor in alkalinity tests (much less than 0.1 meq/L). Consequently, the fact that alkalinity is initially supplied as hydroxide is not to be viewed as problematic, except as it impacts pH (see below).

Limewater that is saturated with calcium hydroxide has a pH of 12.54 at 25ºC. It is actually recognized as a secondary pH standard. The pH is substantially higher at lower temperature (12.627 at 20ºC and 13.00 at 10ºC), and lower at higher temperature (12.289 at 30ºC; 11.984 at 40ºC). Saturated limewater has a conductivity of about 10.3 mS/cm at 25ºC, and contains about 808 ppm of calcium and 40.8 meq/l of alkalinity. Slightly more calcium and alkalinity dissolve at lower temperatures, and less at higher temperatures. Of interest to chemists, a large fraction of the calcium in saturated limewater is present as the ion CaOH+, with the remainder being Ca++. The CaOH+ will instantly dissociate into Ca++ and OH- upon its addition to aquarium water.

Thanks for the response, now that I have a better grasp on the chemistry I'm seeing the error in my current dosing regimen, using kalkwasser as a bandaid for the real problem which seems to be excess CO2.

 

[Randy Holmes-Farley]

Thanks for the response, now that I have a better grasp on the chemistry I'm seeing the error in my current dosing regimen, using kalkwasser as a bandaid for the real problem which seems to be excess CO2.

It's not a band aid. Its one of many good ways to reduce CO2.

 

[Jpcoral]

It's not a band aid. Its one of many good ways to reduce CO2.

Hello Sir,

I just read your article on Kalkwasser. Thank you for your wealth of knowledge.

I read that you purchased 100lb’s for $0.50 a pound some years ago. What vendor did you get your quicklime from? Or what vendor and brand do you recommend today since it has been a while?
Thanks again for your influence in the hobby.
sincerely,

 

[Randy Holmes-Farley]

Hello Sir,

I just read your article on Kalkwasser. Thank you for your wealth of knowledge.

I read that you purchased 100lb’s for $0.50 a pound some years ago. What vendor did you get your quicklime from? Or what vendor and brand do you recommend today since it has been a while?
Thanks again for your influence in the hobby.
sincerely,

Thanks!

We had our local reef club buy a large amount from a distributor for the Mississippi Lime Co. I do not know who the distributor was, but we needed to buy a very large amount. More than any individual would want.

IMO, any food grade material (calcium hydroxide or oxide is fine).

 

[chipmunkofdoom2]

Hello Sir,

I just read your article on Kalkwasser. Thank you for your wealth of knowledge.

I read that you purchased 100lb’s for $0.50 a pound some years ago. What vendor did you get your quicklime from? Or what vendor and brand do you recommend today since it has been a while?
Thanks again for your influence in the hobby.
sincerely,

Not sure where you live, but in the US you can get 6lbs of Ms. Wages' Pickling Lime on Amazon for $22.50. That's $0.25/oz. The 4lb bag of calcium hydroxide from BRS costs over $0.50/oz.