Kalkwasser or two part for me?

Randy Holmes-Farley · Oct 20, 2015

I don't think there's any easy way to distinguish them. Both are white solids easily dissolved in acid.

CaCO3 will bubble in acid, but even a little of it in mostly Ca(OH)2 may bubble. Almost always there will be some CaCO3.

If you have a conductivity probe that can read in the 10 mS/cm range, it is easy to monitor limewater potency. That's how I judge mine.

Ryan15236 · Oct 20, 2015

Glad to see so much information being passed along in this thread. All great info!

Randy I started using the kalkwasser at a dose of 1/4 tsp per gallon of RO water. I actually noticed a drop in Alk and a rise in pH. Does this sound right? My pH went from 8.0 to8.1 and alk 7.7 to 7.2. I went ahead and bumped my alk back up and made a new batch at 1/2 tsp to gallon of RO water.

Randy Holmes-Farley · Oct 20, 2015

The limewater does cause an increase in pH, and if it is not keeping pace with the demand for calcium and alkalinity, you'll notice that first as a drop in alk.

So bumping it up seems appropriate.

black_art · Oct 20, 2015

Dear Randy
can we get Ca(OH)2 by adding CaCO3 to water with following equation?
2 H2O + CaCO3 = Ca(OH)2 + H2CO3

Randy Holmes-Farley · Oct 20, 2015

Nope. That doesn't proceed to the right. It would actually proceed to the left, which is why limewater plus air gives calcium carbonate.

Adding CaCO3 to water gives a very small amount of Ca++ and CO3-- (or 2 HCO3-). It is about 40x less potent (40x less dissolves) than limewater.

I discuss it here:

Chemistry And The Aquarium: Calcium Carbonate As A Supplement ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2002/7/chemistry