kalk question

salty joe

New member
There is enough CO2 in the surrounding air to depress pH in my tank. The tank has a low demand for alk and calcium that is being met with kalk.

When I have corals and a high demand for alk and calcium, If I meet that demand with kalk am I correct to assume the pH will rise if all else is equal?
 

neiltus

New member
How much kalk are you dosing now? If it is a minimal amount like a tenth of a teaspoon per gallon over 2 days, then yes, you will get more of a pH boost from dosing more.

But if your talking about a gallon of saturated water into a tank a day already...well, you at max.

And I imagine every tank/scenario is a little different, right now I dose about 1/3 gallon of fully saturated (2 tsp/gal) kalk a day and my dkh stays around 9.5. I see a small pH change of about .1 better throughout the range of the day vs not using kalk (7.9-8.1). If I drip faster, pH can get a little higher...but I am content with the range I am in.
 

salty joe

New member
I'm dosing kalk slurry. I'm just not sure if I'd get a pH boost with increased kalk even though the additional alk and calcium would be taken up by coral.

The alk and calcium levels in the water with high demand and heavy kalk usage would be the same as now with low demand and low kalk usage.

I think pH would increase, but not sure.

BTW, I plan on using Cupri sorb or poly filter 24/7 as well as my existing algae filter and carbon to handle metal introduced by the kalk.
 

tmz

ReefKeeping Mag staff
Premium Member
I'm dosing kalk slurry. I'm just not sure if I'd get a pH boost with increased kalk even though the additional alk and calcium would be taken up by coral.

CO2 is used when it joins with the (OH)2 from the Ca(OH)2 forming carbonate alkalinity CO3/ HCO3; then the corals use it .So, if the alk increases it does so as a result of the (OH)2 joining with CO2 from the alk using CO2 thus reducing it and raising the pH .

However, when dosing via slurry it's hard to know exactly how much dissolved /disassociated Ca(OH2) is in the slurry given saturation limits and precipitation which will effect the amount of alk actually produced in the process.
 
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salty joe

New member
I was not aware of a heavy metals problem being introduced through the use of Kalk.

There are some decent calculators online...that might help in estimating stuff...

https://www.hamzasreef.com/Contents/Calculators/

I also saw one on pH rise for dose of kalk somewhere, don't remember where.

The metal issue is not there when using clear kalkwasser. I have nowhere near enough evaporation to use kalkwasser.

CO2 is used when it joins with the (OH)2 from the Ca(OH)2 forming carbonate alkalinity CO3/ HCO3; then the corals use it .So, if the alk increases it does so as a result of the (OH)2 joining with CO2 from the alk using CO2 thus reducing it and raising the pH .

.

I think that was a yes...How about clear kalkwasser. Would dosing a lot of kalkwasser in a high demand tank likely result in a higher pH than dosing a little kalkwasser in a low demand tank, even though the alk and calcium levels in the water were the same?
 

tmz

ReefKeeping Mag staff
Premium Member
Quote:
Originally Posted by tmz View Post
CO2 is used when it joins with the (OH)2 from the Ca(OH)2 forming carbonate alkalinity CO3/ HCO3; then the corals use it .So, if the alk increases it does so as a result of the (OH)2 joining with CO2 from the alk using CO2 thus reducing it and raising the pH .

.
I think that was a yes...How about clear kalkwasser. Would dosing a lot of kalkwasser in a high demand tank likely result in a higher pH than dosing a little kalkwasser in a low demand tank, even though the alk and calcium levels in the water were the same?

The alk and calcium levels in the water would not be the same. More kalk would add more alkalinity and more calcium and use more CO2 in the process.
 

salty joe

New member
My plan is to watch alk closely after adding corals and increase kalk to maintain my target of 8 KH. If things go well and the coral grow, I'd have to ramp up kalk additions to stay at 8 KH. Since all that extra alk and calcium is being used by the coral, I wasn't sure if I could expect an increase in pH.
 

neiltus

New member
My plan is to watch alk closely after adding corals and increase kalk to maintain my target of 8 KH. If things go well and the coral grow, I'd have to ramp up kalk additions to stay at 8 KH. Since all that extra alk and calcium is being used by the coral, I wasn't sure if I could expect an increase in pH.

The increase in pH does not go away because the corals are using more. The lime interacting with the CO2 to make carbonate gives the increase in pH.
 

salty joe

New member
The increase in pH does not go away because the corals are using more. The lime interacting with the CO2 to make carbonate gives the increase in pH.

I'm sorry I haven't made myself clear. :hmm2:

My tank now-no corals, low alk demand met by kalk. Alk target of 8 KH. pH is just south of 8.

Same tank in the future-growing corals with a high alk demand met by kalk. Alk target of 8 KH. In the future tank, should I expect a higher pH than my current 7.94-7.98?
 

tmz

ReefKeeping Mag staff
Premium Member
Yes because more CO2 will be used by the the increased kalk to meet the increaed demand for calcium and alk as well as by more photosynthesis from more coral.
 

salty joe

New member
Thanks guys!

Just wondering, what do you consider the top safe range for long term pH?
 
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tmz

ReefKeeping Mag staff
Premium Member
You are welcome .

Seawater is about 8.1. I run 8.2 to 8.35 inlcuding diurnal swing. Randy Farely in one of his articles notes 7.8 to 8.5 is ok ; 8.2 to 8.4 is better . Personally, I'd suggest a max in the 8.4 range; a bit higher might be ok.
 
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