kalk dosing for high demand tanks

[horseplay]

I am dosing 2 parts now and considering adding kalk dosing. Tank currently consumes about 1dkh/day of alkalinity.

As I understand the ph for fully saturated kalk solution is about 12. Assuming dosing 1 gal of this solution to 100 gal of total water volume per day. If simple math can be used here it will have a minimal effect to PH as it only adds 1% of the water volume. Does it still make sense to dose kalk purely for the benenit of raising PH?

 

[nereefpat]

1 dKH per day will be close to the limit that kalk can replenish. As an example, a 100 gallon system that needs 1 dKH dosed per day via kalk would be a little less than a gallon of saturated limewater, which may be getting close to evaporation levels.

As to the math and pH, here's a quick quote from RHF. I'm sure he won't mind:
"Adding 1.25% of the tank volume with saturated limewater will boost the pH instantly by about 0.7 pH units, but the effect rapidly wanes as the system pulls in more CO2 from the air."

 

[horseplay]

Thanks for answering the other question that I didn't ask which is how much max dkh can kalk replenish.

The ph change is interesting, which is not linear. I see this with my 2-parts dosing, the ph rises then drops quickly within the next 30 mins or so. and I dose in the return chamber.

So this begs the question, where is the ph raising benefit everyone's raving about?

 

[Randy Holmes-Farley]

I am dosing 2 parts now and considering adding kalk dosing. Tank currently consumes about 1dkh/day of alkalinity.

As I understand the ph for fully saturated kalk solution is about 12. Assuming dosing 1 gal of this solution to 100 gal of total water volume per day. If simple math can be used here it will have a minimal effect to PH as it only adds 1% of the water volume. Does it still make sense to dose kalk purely for the benenit of raising PH?

Nope, that analysis is not remotely accurate. Lol

It ignores the fact that pH is logarithmic so pH 12.54 in saturated kalkwasser has 22,000 times more OH- and 22,000 lower H+ than does seawater at pH 8.2. simple math would say adding pH 12.54 to pH 8.2 will skyrocket the pH to above 10.5, even adding only 1% by volume.

But even that analysis ignores the strong pH buffering effects of ions such as bicarbonate that limit the rise.

As to the effect, it is noted above and whether that is useful or not depends on your circumstances.

 

[MarineandReef Jaron]

I won't try to do the math but I will give some personal experience. My current tank is low demand but my best tank I have had was a 120 gallon mixed reef. I could dose about a gallon and a half of kalk a day and still not exceed my evap rate. Before switching to kalk my pH hovered around 7.7-8.0 after kalk the pH stayed around 8.0-8.3. In one sense this only boosted the average pH by.3 but that .3 was all that was needed to get the pH into the ideal range.

There is also an interesting feedback loop that can come from kalk. For example, adding kalk maintains alkalinity while increasing pH. The increased pH increases coral calcification / growth rates which increases kalk demand, and then further increases pH further which further increases growth etc. (More corals also = more Photosynthesis which leads to less CO2)

Sometimes the pH increase that we realize is greater than what we would believe would be possible from the simple chemical reaction alone based on the feedback loop.

 

[horseplay]

Nope, that analysis is not remotely accurate. Lol

It ignores the fact that pH is logarithmic so pH 12.54 in saturated kalkwasser has 22,000 times more OH- and 22,000 lower H+ than does seawater at pH 8.2. simple math would say adding pH 12.54 to pH 8.2 will skyrocket the pH to above 10.5, even adding only 1% by volume.

But even that analysis ignores the strong pH buffering effects of ions such as bicarbonate that limit the rise.

As to the effect, it is noted above and whether that is useful or not depends on your circumstances.

Yeah it makes a lot sense if it's logarithmic. Thanks for replying Randy.

 

[horseplay]

I won't try to do the math but I will give some personal experience. My current tank is low demand but my best tank I have had was a 120 gallon mixed reef. I could dose about a gallon and a half of kalk a day and still not exceed my evap rate. Before switching to kalk my pH hovered around 7.7-8.0 after kalk the pH stayed around 8.0-8.3. In one sense this only boosted the average pH by.3 but that .3 was all that was needed to get the pH into the ideal range.

There is also an interesting feedback loop that can come from kalk. For example, adding kalk maintains alkalinity while increasing pH. The increased pH increases coral calcification / growth rates which increases kalk demand, and then further increases pH further which further increases growth etc. (More corals also = more Photosynthesis which leads to less CO2)

Sometimes the pH increase that we realize is greater than what we would believe would be possible from the simple chemical reaction alone based on the feedback loop.

Thanks for sharing this. What is your dosing schedule like? I am thinking about getting a kalk stirrer.

 

[MarineandReef Jaron]

Just got a new IceCap stirrer for my current tank but it is yet to go online. In the past I have always. used a peristaltic pump to pump through a kalk reactor and dose hourly. You can start by measuring Alk demand and using a dosing calculator to find the dose, or you can match your makeup water with kalk and make up extra demand with 2 part if your demand is greater than the evap rate.

 

[horseplay]

Thanks. I did a calculation it will take 0.7 gal to raise 1dkh for my tank volumn. 0.7 gal is close to my evaporation rate in winter. In the summer the tank loses about 1 liter/day.

 

[Randy Holmes-Farley]

Thanks. I did a calculation it will take 0.7 gal to raise 1dkh for my tank volumn. 0.7 gal is close to my evaporation rate in winter. In the summer the tank loses about 1 liter/day.

When limewater/kalkwasser is limited by evaporation, you can use a DIY two part that has the same pH raising effect per unit of alk added:

Second New DIY Two Part Recipe with Higher pH Boost

In a previous thread, I posted a true two part DIY recipe: https://www.reef2reef.com/threads/new-diy-two-part-recipes-with-higher-ph-boost.344500/ But some folks may want to just swap the new ingredient into my 2/3 part recipe (as used by BRS, for example). Here's the original recipe link...

www.reef2reef.com

 

[nereefpat]

I know it says it in the article in bold, but be very careful with lye/caustic soda (sodium hydroxide), if you go that route. It definitely will raise alk and pH, and it has many other great uses in industry and even around the house, but most people aren't used to or trained to handle those kind of chemicals. Treat it like battery acid, but a base instead.