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Mikser Aqua Special KALKMIXER otherwise known as a lime water mixer is used for automated production and dosing of lime water (Kalkwasser) and refilling evaporated water from the aquarium.
The mixer can be connected to the Aqua Special's Water Level Controller. The lime water, otherwise known as calcareous water, or in German, Kalkwasser, is a saturated solution of calcium hydroxide or calcium oxide in water.
In the aquarium, the hydroxide reacts with the dissolved carbon dioxide and produces hydrogen

OH- + CO2 = HCO3-

If Kalkwasser is added too quickly, hydroxide can react with hydrogen and the formation of calcium carbonate, which is almost insoluble. As a result of such a reaction alkalinity drops.

Ca2+ + HCO3- + OH- = H2O + CaCO3

For this reason, we recommend pouring Kalkwasser to the aquarium at night through the kalkmixera, when the pH is relatively at its lowest, the concentration of carbon dioxide at its highest.
An important advantage of using Kalkwasser is the precipitation of phosphates. As a result, the following reaction produces nearly insoluble hydroxylapatite

3 Ca3(PO4)2 . Ca(OH)2 = Ca10(PO4)6(OH)2

It is worth noting that if the pH of Kalkwasser drops from 12.4 to 12.2, the concentration of calcium decreases from 900 ppm to 300 ppm. This happens when the solution is in contact with the carbon dioxide in the atmosphere. Using the Aqua Special Kalk Stirrer reduces contact with atmospheric carbon dioxide to a minimum.
The design of our Kalk Stirrer is such that an electric motor, or a stepper motor (depending on model), is used to move the stirring arm. With this method, none of the mechanical parts have contact with the lime water, and thus do not petrify.


Adding a saturated solution of calcium hydroxide was the first way of equalize calcium in reef aquariums. First, calcium hydroxide powder mixes with osmotic water. Undissolved hydroxide eventually settles on the bottom, and a transparent solution moves to the top of the container, which then is slowly added to the aquarium, that is the Kalkwasser or lime water. There is no chemical difference if one uses a calcium oxide or calcium hydroxide.
It is much easier to handle the calcium oxide because of its gravel like consistency, but calcium hydroxide is dissolved much more easily than calcium oxide, which simply means that the calcium oxide requires more effort during mixing. However, calcium oxide releases heat when it is dissolved in water.

Ca(OH)2 + H2O Ca2+ + 2OH-

When carbon dioxide and hydrogen ions bind after the addition of Kalkwasser to the aquarium, they create bicarbonate.

OH- + CO2 HCO3 -

When hydroxide ions bind with bicarbonate ions after the addition of Kalkwasser to the aquarium, carbonate ions and water are created.

OH- + HCO3 - CO32- + H2O

Due to the very high pH value of the solution at about 12.4, it is recommended to dose by drops using the Kalk Stirrer to avoid a dangerous increase of the pH levels in the aquarium. The solution easily reacts with carbon dioxide from the atmosphere and as a result of this reaction, calcium carbonate is created which is very hard to dissolve in water and forms a sediment.


More and more marine aquarists use a Kalk Stirrer in conjunction with a Calcium Reactor. Kalk Stirrer produces carbon dioxide, and in some cases, the phosphates are bound by Kalkwasser. Using these devices one should be careful not to overdosecalcium. Quick dosing during the day becomes problematic.


Calcium concentration in natural seawater is about 400 mg / L. In areas near coral reefs, sea water has a tendency to slightly increase the level of calcium from about 420 to as high as 480 mg / L. It simply means that the aquarist should seek to maintain the level of calcium in the reef aquarium to a close of 400 mg / L at a specific gravity of 1.025 at. Comparisons of measurements of calcium ion concentration in seawater must include the level of salinity (or specific gravity), because the calcium concentration increases with increasing salinity, and vice versa.


Alkalinity is a general term that includes the number of compounds, which together allow water to buffer the effect of lowering the pH of the acid (hydrogen ions, H +). These compounds contain bicarbonate, carbonate, boron, silicate, hydroxide, and even phosphate. Taken together, these compounds represent the total alkalinity of seawater. Despite the fact that other compounds contribute to the alkalinity of sea water, bicarbonate and carbonate are the most important simply because bicarbonate accounts for 90% of the total alkalinity, and carbonate for 7%, total alkalinity of natural seawater is between 2.1 and 2.5 meq / L (6 - 7 dKH). In aquaria, which received a very small amount of alkalinity supplements, the values may be as low as 1.0 meq / L (2.8 dKH)..


When you add calcium and alkalinity do not forget to add the same proportion as they are used in the manufacture of carbonate calcification. The precipitation of calcium carbonate uses its two components in the exact ratio of 1:1. This corresponds to one meq / L (2.8 dKH, the equivalent of 50 ppm CaCO3) for each 20 ppm of calcium.




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