Saturated limewater

kevensquint · Jan 19, 2017

Hello, from reading Randy's articles and testing with reef calculators. It seems that dosing limewater raises Ph more significantly than Ca and Alk. For example, my tank has about 125 gallons of water, I need to boost Alk 0.2 dkh / day (atm). However my Ph is a bit low for my liking. It is 8.1 day, 7.9 night. Is it true I can use limewater to boost ph by 0.05 or 0.1 before overshooting my daily Alk consumption? I could not find data on X amout of limewater= a ph boost of X anywhere. Thanks.

JimWelsh · Jan 19, 2017

I think the answer to your question may be found in Randy's article(s) about elevated pH more than ones about limewater, e.g. http://reefkeeping.com/issues/2005-03/rhf/#6. The reason there is no calculator for this is probably because the elevated pH effect is temporary, and depends upon how much the tank is aerated, and how long it takes the tank to reach equilibrium with the ambient atmosphere's CO2 level.

Brew12 · Jan 19, 2017

kevensquint said:
I could not find data on X amout of limewater= a ph boost of X anywhere. Thanks.

You cannot find the information because it isn't quite that simple. The reason is that it is greatly dependent on the amount of CO2 in your system that influences your pH equilibrium equation. Here is how it works.

The CO2 in the tank combines with the water to form Carbonic acid which drives down pH.
CO2+H2O -> H2CO3

If you add CO2, it shifts the equation to the left and lowers pH. When you add Kalk {Ca(OH)2} it dissociates into CA + 2OH. The OH reacts with the carbonic acid (H2CO3) to become bicarbonate which shifts the equation to the right and raises pH. OH + H2CO3 -> 2HCO3

pH is an equilibrium reaction in a tank between carbonic acid, bicarbonate, and carbonate.

H2CO3 <-> H + HCO3 <-> 2H + CO3
Acid <---------------------> Base

kevensquint · Jan 19, 2017

I see, the reef calulator states at 1L of limewater in 125 gallons to raise Alk 0.2dkh....ph substantially higher. I took this as an indication that significantly less, would not effect Alk yet still boost ph

Randy Holmes-Farley · Jan 19, 2017

kevensquint said:
Hello, from reading Randy's articles and testing with reef calculators. It seems that dosing limewater raises Ph more significantly than Ca and Alk. For example, my tank has about 125 gallons of water, I need to boost Alk 0.2 dkh / day (atm). However my Ph is a bit low for my liking. It is 8.1 day, 7.9 night. Is it true I can use limewater to boost ph by 0.05 or 0.1 before overshooting my daily Alk consumption? I could not find data on X amout of limewater= a ph boost of X anywhere. Thanks.

Adding 1.25% of the tank volume in saturated limewater will instantly boost the pH by about 0.7 pH units, alk by 0.5 meq/L (1.4 dKH) and calcium by 10 ppm.

The pH effect drops as CO2 is pulled into the tank. How fast depends on how well aerated it is.

kevensquint · Jan 19, 2017

Thank you for your time.

Randy Holmes-Farley · Jan 20, 2017

You're welcome.

Happy Reefing.

kevensquint · Jan 22, 2017

Hi Randy, I read that limewater has the effect of precipitation of metals. Question: what about Mg and K? Since 3 days I have been adding 250ml of limewater each night to about 125 gallons of reef water. At the same time my Mg and K have dropped some. Enough for me to dose those to bring them back. Is it coincidence? Or the Limewater dosing IYO? Thanks

Randy Holmes-Farley · Jan 23, 2017

kevensquint said:
Hi Randy, I read that limewater has the effect of precipitation of metals. Question: what about Mg and K? Since 3 days I have been adding 250ml of limewater each night to about 125 gallons of reef water. At the same time my Mg and K have dropped some. Enough for me to dose those to bring them back. Is it coincidence? Or the Limewater dosing IYO? Thanks

It precipitates them in the limewater, but not so much in the aquarium. It has no impact on potassium in either location, but magneisum is almost totally insoluble in limewater.

Limewater is not the cause of low magnesium except that it adds calcium and alkalinity and does not replace magnesium that also slowly declines.