Saltwater Aquarium Guide -- Fast Facts

	Fast Facts (page 24) Why does adding a little vinegar to Kalkwasser help in the reef building? When Calcium Hydroxide solution (Kalkwasser) is slowly dripped into your aquarium, it captures free Carbon Dioxide present in the tank water and converts it to Bicarbonate ions (which is a good thing), like this:
	Ca++ + 2(OH-) + 2(CO2) <==> Ca++ + 2(HCO3-)

	If you drip too fast or if there is not enough Carbon Dioxide available in the water, your shiny new Bicarbonate ions will be converted to Carbonate ions (a bad thing), like this:
	Ca++ + 2(OH-) + 2(HCO3-) <==> Ca++ + 2(CO3--) + 2 H2O

	The Carbonate ions formed will make the Ca++ you are trying to add to the tank get wasted by the useless precipitation of Calcium Carbonate. So, too rapid addition of Kalk may actually cause the Calcium and Alkalinity in your tank to go DOWN instead of UP (a bad thing), like this:
	Ca++ + 2(HCO3-) + Ca++ + 2(OH-) <==> 2 CaCO3 + 2 H2O

	In the above reaction, a Calcium ion and two Bicarbonate ions from the aquarium combine to form solid calcium carbonate, the white stuff you get in your tank, which is really just a kind of sand. This can happen even with a slow drip of Kalk if there is not enough CO2 in your water, something you can't easily control. Try mixing and adding your Kalkwasser as follows: Pour 15ml of 5% Acetic Acid (or ordinary Distilled White Vinegar from the grocery store same thing) into a 1 liter (1 quart) container. Dissolve 1/2 teaspoon of lab-grade Ca(OH)2 (or commercial Kalkwasser mix) in the Acetic Acid, and then dilute to 1 liter (1 quart) volume with either RO/DI water, or even tank water. more---->



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