Calculating starting kalkwasser dosage in terms of alkalinity?

[drawman]

I have toyed around with the idea of switching to kalkwasser from 2 part on my SPS frag tank. Demand is relatively low so I think it would fulfill my needs and I would like to dose from my BRS 1.1mL doser if I do switch. It's odd to me that I can't find any information relating dosing saturated kalkwasser in terms of alkalinity but I assume that is due to the fact that most people use it in top off situations.

I'm curious though if I make a saturated solution of limewater (ie 2tsp/gallon), then let it settle can I calculate how much I would need to dose of this solution every 24 hours to keep alkalinity stable? I'm not sure if the amount of dissolved kalk in this solution would be consistent through all temperatures, elevation, etc. that is well beyond me.

I would likely use BRS Kalkwasser but from Seachem's website it says adding 1 gallon of saturated kalkwasser solution to 40 gallons of aquarium water will increase calcium by 24mg/L. Since 1dKh is equal to 6.4-7.1ppm Ca I'm assuming I could use this to calculate a starting dose? Anyone see any issue with this? I can do the math from there but I'm surprised I haven't seen a calculator relating this.

Really for me the most important thing is keeping alkalinity stable but I would like this tank to benefit from an increase in pH to hopefully fuel coral growth.

 

[Randy Holmes-Farley]

You can use this calculator (use entry for limewater):

http://reef.diesyst.com/chemcalc/chem_calc3.html

[edited] Adding 1.25% of the total volume will add 0.5 meq/L of alkalinity (1.4 dKH) and 10 ppm of calcium.

 

[drawman]

Here will be my calculation for anyone who cares:

Seachem's website says 1 gallon (or 3.785L) of this saturated solution (2tsp/gallon) will raise 150L (40 gallons) of tankwater by 24mg/L (or ppm). To simplify I could say that this solution will raise 100L of tank volume by 36mg/L.

1dKh of Alkalinity is equal to about 6.4-7.1mg/L of Calcium. So this solution will raise 100L of tank volume by somewhere between 5.04 to 5.6 dKH (take 36/6.4 and 36/7.1).

Divide those total values by 3.785L and further divide that by 1000mL/L then you can see how much each mL of saturated solution will raise the dKH. Each mL of solution should raise alkalinity in 100L of tank water by somewhere between 0.001331 to 0.001479 dKH.

 

[Randy Holmes-Farley]

lol

 

[drawman]

You can use this calculator (use entry for limewater):

http://reef.diesyst.com/chemcalc/chem_calc3.html

Adding 1.25% of the total volume will add 1 meq/L of alkalinity (2.8 dKH) and 20 ppm of calcium.

Thanks as always Randy! I just went on a math tear before you posted that. Proves my googling skills just aren't up to par ha.

 

[drawman]

So @Randy Holmes-Farley I'm thinking about getting this going on my tank that is around 30 gallons of volume.

I figure that if I dose at night I will start off around 6.25mL/every hour for 8 hrs.

If I dose for the full 24 hrs then it would be 2.08mL/every hour.

Do either of these scenarios sound reasonable (ie pH impact not too bad?)

 

[michaelrappuhn]

You can use this calculator (use entry for limewater):

http://reef.diesyst.com/chemcalc/chem_calc3.html

Adding 1.25% of the total volume will add 1 meq/L of alkalinity (2.8 dKH) and 20 ppm of calcium.

Hi Randy, I get 2.45/100 = 2.45% not 1.25% for 2.8 dKH, can you show me what I am doing wrong?

 

[Randy Holmes-Farley]

Sorry, my mistake.

Should have said:

Adding 1.25% of the total volume will add 0.5 meq/L of alkalinity (1.4 dKH) and 10 ppm of calcium.

 

[michaelrappuhn]

Sorry, my mistake.

Should have said:

Adding 1.25% of the total volume will add 0.5 meq/L of alkalinity (1.4 dKH) and 10 ppm of calcium.

Thanks for the quick reply!

 

[MrWanted]

Sorry, my mistake.

Should have said:

Adding 1.25% of the total volume will add 0.5 meq/L of alkalinity (1.4 dKH) and 10 ppm of calcium.

Dear Randy

This means 10 ppm calcium and 25 ppm alkalinity. Shouldn't be 20 ppm alkalinity?

Ca(OH)2 = Kalkwasser
OH- + CO2 = HCO3 = Bicarbonate

And what happens with the excess alkalinity? Don't we consue equal amount of calcium and alkalinity in the tank?

 

[Randy Holmes-Farley]

Dear Randy

This means 10 ppm calcium and 25 ppm alkalinity. Shouldn't be 20 ppm alkalinity?

Ca(OH)2 = Kalkwasser
OH- + CO2 = HCO3 = Bicarbonate

And what happens with the excess alkalinity? Don't we consue equal amount of calcium and alkalinity in the tank?

Im not measuring alk in ppm in my post.

there is no excess alk. There actually is a tiny excess of calcium in kalkwasser.

Calcium carbonate contains one mole of calcium and two moles of alkalinity.

Extending what you wrote:


Ca(OH)2 = Kalkwasser = Ca++ + 2OH-
OH- + CO2 = HCO3 = Bicarbonate
OH- + HCO3- = H2O (water) + CO3– (carbonate)
Ca++ + CO3– = CaCO3

Adding the equations together we get:

Ca(OH)2 + CO2 = H2O (water) + CaCO3


The reason it is not perfectly balanced is that in seawater, a little magnesium and strontium get into the calcium carbonate, so a little less than 1:1 calcium to carbonate is used.

 

[Reefahholic]

Kalk is pretty weak, but it’s magical unicorn juice! No kidding!

To put it into perspective BRS 2-part and Randy’s DIY 2-part recipe #1 are both 5300 dKH/L.

Fully saturated Kalk is somewhere around 114 dKH. Randy can double check that, but it’s pretty weak stuff.

I always start low and find myself up to 500 mL’s very quickly on 100/G system. Like in the first week. So if you’re switching from 2-part you’ll being dosing a lot more even if you came from Aquaforest, but I never dose it alone. I always dose on top of 2-part or my calcium reactor.

 

[WirelessMike]

Sorry, my mistake.

Should have said:

Adding 1.25% of the total volume will add 0.5 meq/L of alkalinity (1.4 dKH) and 10 ppm of calcium.

When I get the meq/l and ppm numbers on the calculator how do I determine the amount I would dose every hour? Sorry I’m not a math wizard but I’m trying to get better.

 

[Randy Holmes-Farley]

When I get the meq/l and ppm numbers on the calculator how do I determine the amount I would dose every hour? Sorry I’m not a math wizard but I’m trying to get better.

If you know the alk you want to dose daily in ppm or dKH or meq/L, then enter the tank volume, and start guessing volumes of limewater (kalkwasser) and calculate see what it gives. Start at your daily amount of evaporation. It won't be perfect, so then try a second guess. Then home in on the right volume by making a next guess, etc.

 

[WirelessMike]

If you know the alk you want to dose daily in ppm or dKH or meq/L, then enter the tank volume, and start guessing volumes of limewater (kalkwasser) and calculate see what it gives. Start at your daily amount of evaporation. It won't be perfect, so then try a second guess. Then home in on the right volume by making a next guess, etc.

Thanks Randy! I appreciate the guidance

 

[Randy Holmes-Farley]

You're welcome.

Let us know if you need more assistance.

 

[stlamarc]

Kalk is pretty weak, but it’s magical unicorn juice! No kidding!

To put it into perspective BRS 2-part and Randy’s DIY 2-part recipe #1 are both 5300 dKH/L.

Fully saturated Kalk is somewhere around 114 dKH. Randy can double check that, but it’s pretty weak stuff.

I always start low and find myself up to 500 mL’s very quickly on 100/G system. Like in the first week. So if you’re switching from 2-part you’ll being dosing a lot more even if you came from Aquaforest, but I never dose it alone. I always dose on top of 2-part or my calcium reactor.

Can I ask what's the reason for dosing 2-part on top of Kalkwasser? I just switched to using Kalkwasser and find that it takes A LOT of Kalk solution to get the same result I had with 2-part. But why would you do both?

 

[Reefahholic]

Can I ask what's the reason for dosing 2-part on top of Kalkwasser? I just switched to using Kalkwasser and find that it takes A LOT of Kalk solution to get the same result I had with 2-part. But why would you do both?

Kalk elevates pH. It has a pH of 12.4. It will significantly raise pH going into a tank that’s sitting at 7.8-8.0 depending on the frequency and amount dosed. Sometimes as much as 0.2+ pH units.

 

[Randy Holmes-Farley]

Can I ask what's the reason for dosing 2-part on top of Kalkwasser? I just switched to using Kalkwasser and find that it takes A LOT of Kalk solution to get the same result I had with 2-part. But why would you do both?

The primary reason some use both is that kalkwasser is limited in volume per day by the daily evaporation rate, and that volume may not supply enough calcium and alk to many aquaria. Thus, some folks use other methods in addition to kalkwasser.

 

[stlamarc]

The primary reason some use both is that kalkwasser is limited in volume per day by the daily evaporation rate, and that volume may not supply enough calcium and alk to many aquaria. Thus, some folks use other methods in addition to kalkwasser.

I've ran into that issue myself and decided to stop using Kalkwasser and went back to 2-PART only. I didn't see the point of dosing multiple solutions and using multiple dosing head to get the same results. To explain: I had to use several dosing heads for Kalk because each head was limited to 1000ML per day.