Pros and Cons of Alkalinity and Calcium Dosing Methods

[rishma]

@Randy Holmes-Farley - thank you! Holy smokes, that was more complicated than I anticipated. I chuckled at the sentence…So now we can use that answer to easily determine the over-addition of calcium. Reminded me of a professor.

Would appreciate if you can check some math and logic for me.

For the RMM method I’ve used 2230 ml of kalkwasser in a 100L system adds 20 mg/L of calcium and 1 meq/L alkalinity. (I used the Hamza reef calculator for that but I later checked the J. Dieck reef calculator and it said 2450 ml, I’m not sure which is correct).

So that would be 2000 mg of calcium and 3000 mg of alkalinity added to a 100L tank.

If the demand ratio is more like 3000 alk to 1750 Ca then I need an extra alkalinity to be balanced with the extra 250 mg of calcium. That would be 3000/1750 x 250 =428.6 mg of additional alkalinity needed.

Then I’d add the amount of baking soda or other product to balance it out. Unfortunately, as you previously pointed out to me, the chemistry of kalkwasser is inconvenient so I cannot just add it to the mix and would have to dose separately.

Sound right?

 

[BryanM]

I might just add that the powder version of AFR is around $7/L, quite a bit more affordable than the liquid, even if a pain to mix.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley - thank you! Holy smokes, that was more complicated than I anticipated. I chuckled at the sentence…So now we can use that answer to easily determine the over-addition of calcium. Reminded me of a professor.

Would appreciate if you can check some math and logic for me.

For the RMM method I’ve used 2230 ml of kalkwasser in a 100L system adds 20 mg/L of calcium and 1 meq/L alkalinity. (I used the Hamza reef calculator for that but I later checked the J. Dieck reef calculator and it said 2450 ml, I’m not sure which is correct).

So that would be 2000 mg of calcium and 3000 mg of alkalinity added to a 100L tank.

If the demand ratio more like 3000 alk to 1750 Ca then I need an extra alkalinity to be balanced with the extra 250 mg of calcium. That would be 3000/1750 x 250 =428.6 mg of additional alkalinity needed.

Then I’d add the amount of baking soda or other product to balance it out. Unfortunately, as you previously pointed out to me, the chemistry of kalkwasser is inconvenient so I cannot just add it to the mix and would have to dose separately.

Sound right?

The potency difference between calculators might be a temperature issue for what saturation is attained, but at 25 deg C, kalkwasser at full saturation is a known pH standard and contains ~ 0.0204 M calcium, and 0.0408 eq of alkalinity. ~816 ppm (mg/L) calcium. More dissolves at lower temp. Might also be an error in one of them.

2.230 Liters of kalk adds 1.82 grams of calcium.

If we assume the excess calcium is 10% (I calculated 12% in the above data, but 10% is close enough and may be more accurate in a heavy coral tank) then the excess calcium is 0.18 grams calcium.

0.18 grams of calcium combines with about 1.5 times as much carbonate (0.27 g) to make pure calcium carbonate. That amount is present in 0.48 grams of sodium carbonate.

Thus, you'd add roughly a half gram of sodium carbonate per day.

I'd use less if coralline is not a main component of alk demand.

 

[Randy Holmes-Farley]

I might just add that the powder version of AFR is around $7/L, quite a bit more affordable than the liquid, even if a pain to mix.

Yes, it is certainly true that one can reduce the costs of some of these by starting with powders or using larger containers.

AFR powder is not cheaper than carbocalcium (the alk and calcium part of AFR), so it will still be orange in the charge (but not red).

 

[rishma]

The potency difference between calculators might be a temperature issue for what saturation is attained, but at 25 deg C, kalkwasser at full saturation is a known pH standard and contains ~ 0.0204 M calcium, and 0.0408 meq of alkalinity. ~816 ppm (mg/L) calcium. More dissolves at lower temp. Might also be an error in one of them.

2.230 Liters of kalk adds 1.82 grams of calcium.

If we assume the excess calcium is 10% (I calculated 12% in the above data, but 10% is close enough and may be more accurate in a heavy coral tank) then the excess calcium is 0.18 grams calcium.

0.18 grams of calcium combines with about 1.5 times as much carbonate (0.27 g) to make pure calcium carbonate. That amount is present in 0.48 grams of sodium carbonate.

Thus, you'd add roughly a half gram of sodium carbonate per day.

I'd use less if coralline is not a main component of alk demand.

Thanks you. I’m a little lost in the units I think. Perhaps I need another cup of coffee. I don’t do much math these days.

Regarding this statement… full saturation is a known pH standard and contains ~ 0.0204 M calcium, and 0.0408 meq of alkalinity. ~816 ppm (mg/L) calcium.

So 816 mg/L Ca means 2450 ml of Kalk added to a 100L tank will add 20 ppm (mg/L) calcium. Is that also adding 1 meq/L (2.8 dKH) and alkalinity? I don’t understand the 0.0408 meq of alkalinity.

 

[Randy Holmes-Farley]

Thanks you. I’m a little lost in the units I think. Perhaps I need another cup of coffee. I don’t do much math these days.

Regarding this statement… full saturation is a known pH standard and contains ~ 0.0204 M calcium, and 0.0408 meq of alkalinity. ~816 ppm (mg/L) calcium.

So 816 mg/L Ca means 2450 ml of Kalk added to a 100L tank will add 20 ppm (mg/L) calcium. Is that also adding 1 meq/L (2.8 dKH) and alkalinity? I don’t understand the 0.0408 meq of alkalinity.

Sorry, the alk should have read 0.0408 eq of alkalinty, not meq. That is 40.8 meq. Put that in 100 L, and it boosts alk by 2.45 l X 0.408 meq/L, or 2.8 dKH.

816 mg/L of calcium x 2.45 Liters dosed / 100 L final volume = 20 ppm calcium.

 

[rishma]

Sorry, the alk should have read 0.0408 eq of alkalinty, not meq. That is 40.8 meq. Put that in 100 L, and it boosts alk by 2.45 l X 0.408 meq/L, or 2.8 dKH.

816 mg/L of calcium x 2.45 Liters dosed / 100 L final volume = 20 ppm calcium.

Thank you for patiently walking through that with me. I’m going to ponder this some more.

 

[Randy Holmes-Farley]

Thank you for patiently walking through that with me. I’m going to ponder this some more.

Happy to explain more if its confusing.

 

[Corolling]

Hi Randy, great post! As for the cost, I'm under the understanding that esv although most expensive, has more trace elements in it from the factory. Also, I read on esv website that you shouldn't have to add mag since alk and cal mixture has it already. Any truth to that?

 

[smallcrpt]

I know you said you have your kalk mix in your ATO set up. Have you had to replace your pumps over time faster than what would be considered normal?

 

[Randy Holmes-Farley]

Hi Randy, great post! As for the cost, I'm under the understanding that esv although most expensive, has more trace elements in it from the factory. Also, I read on esv website that you shouldn't have to add mag since alk and cal mixture has it already. Any truth to that?

I address those issues here, but the upshot is you need more trace elements if you intend to offset demand:

How a Two Part Alkalinity and Calcium System Works, and Why it Matters

How a Two Part Alkalinity and Calcium System Works, and Why it Matters By Randy Holmes-Farley This article is intended to help aquarists understand some of the important differences between the great variety of two and three part alkalinity and...

www.reef2reef.com

 

[Randy Holmes-Farley]

I know you said you have your kalk mix in your ATO set up. Have you had to replace your pumps over time faster than what would be considered normal?

I used a diaphragm pump that lasted as long as I used it (many years).

 

[Koty]

Thank you very much, Randy, for this great article (It should be a chapter in a book ).
You accurately distilled all the pros and cons of all dosing methods.
With the three-part Balling system, there are annoying salinity and Ca creep-ups (Especially to no WC tanks)
Can the latter be fixed by adding MgCl2 and maybe even StCl2 to the Ca container based on known rations in the coral skeleton? I understand that every tank is different and many critters precipitate Ca/Alk, but this will at least minimize the Ca creep-up. Another idea is to dilute the CaCl2 relative to the alkalinity concentration (This will slightly mess with the Na/Cl Ratios that the 3rd container should compensate for).
Thanks

 

[rishma]

The potency difference between calculators might be a temperature issue for what saturation is attained, but at 25 deg C, kalkwasser at full saturation is a known pH standard and contains ~ 0.0204 M calcium, and 0.0408 eq of alkalinity. ~816 ppm (mg/L) calcium. More dissolves at lower temp. Might also be an error in one of them.

2.230 Liters of kalk adds 1.82 grams of calcium.

If we assume the excess calcium is 10% (I calculated 12% in the above data, but 10% is close enough and may be more accurate in a heavy coral tank) then the excess calcium is 0.18 grams calcium.

0.18 grams of calcium combines with about 1.5 times as much carbonate (0.27 g) to make pure calcium carbonate. That amount is present in 0.48 grams of sodium carbonate.

Thus, you'd add roughly a half gram of sodium carbonate per day.

I'd use less if coralline is not a main component of alk demand.

Ok, I thought about this some more. To make it simple for those of us using kalkwasser and/or AFR with excess calcium, to keep calcium from creeping up we could dose about 10% of our alkalinity with an alkalinity-only source like sodium carbonate.

Do I have that right?

 

[Randy Holmes-Farley]

Ok, I thought about this some more. To make it simple for those of us using kalkwasser and/or AFR with excess calcium, to keep calcium from creeping up we could dose about 10% of our alkalinity with an alkalinity-only source like sodium carbonate.

Do I have that right?

Yes, with the amount (5%, 10%, etc) depending mostly on the degree of coralline growth relative to hard corals (and water changes). As I’ve noted, I solved the problem by just doing normal water changes with a lower calcium salt mix.

 

[Randy Holmes-Farley]

Thank you very much, Randy, for this great article (It should be a chapter in a book ).
You accurately distilled all the pros and cons of all dosing methods.
With the three-part Balling system, there are annoying salinity and Ca creep-ups (Especially to no WC tanks)
Can the latter be fixed by adding MgCl2 and maybe even StCl2 to the Ca container based on known rations in the coral skeleton? I understand that every tank is different and many critters precipitate Ca/Alk, but this will at least minimize the Ca creep-up. Another idea is to dilute the CaCl2 relative to the alkalinity concentration (This will slightly mess with the Na/Cl Ratios that the 3rd container should compensate for).
Thanks

Calcium creep should not be an issue with a 2 or three part, but if it is, can you just use less if the calcium part?

 

[Koty]

Yes. that will work however, it makes a mess with the routine of filling and preparing the solutions. I guess I will use a slightly diluted CaCl2 to slowly reduce the Ca back to natural levels.

 

[Randy Holmes-Farley]

Yes. that will work however, it makes a mess with the routine of filling and preparing the solutions. I guess I will use a slightly diluted CaCl2 to slowly reduce the Ca back to natural levels.

That would also work.

What two part are you using?

 

[smallcrpt]

Yes, with the amount (5%, 10%, etc) depending mostly on the degree of coralline growth relative to hard corals (and water changes). As I’ve noted, I solved the problem by just doing normal water changes with a lower calcium salt mix.

I'm currently doing AWC with tropic Marin salt and my calcium has been creeping higher. If I switch to IO, do you recommend dosing trace elements? Or should they be ok with kalk and io?
I was using io Orange bucket but thought the fancy TM salt would help with growth.

 

[Randy Holmes-Farley]

I'm currently doing AWC with tropic Marin salt and my calcium has been creeping higher. If I switch to IO, do you recommend dosing trace elements? Or should they be ok with kalk and io?
I was using io Orange bucket but thought the fancy TM salt would help with growth.

How are you dosing alk and calcium?