Pro & Contra - Kalkwasser vs. Reactor
I want to try to explain the general mechanisms and effects of kalkwasser and calcium reactors.
Kalkwasser sounds for the most reefer very promising and should be so easy and inexpensive to use. If one looks whole closer, a mostly unexpected view arises.
What are actually the components of kalkwasser? Take osmosis water and calcium hydroxide, stems and leaves several times to the mixture. After a short time, the liquid must become clear, one gives them in the aquarium. Was that all? Is it that simple? What actually happened and what is calcium hydroxide for a non-chemist? A lot of questions which must be answered.
Simplified, Calcium hydroxide is a substance from calcium (Ca), oxygen (O) and hydrogen (H). Oxygen and hydrogen are firmly connected, the result is hydroxide (OH). This OH ion is very basic (alkaline) and has a pH of 14. Two of these are firmly connected with one calcium ion (Ca).
Calcium hydroxide is: Ca(OH)2
If Calciumhydroxid is given in water, a part of the connection breaks up, it is solved. Then from Calciumhydroxid becomes a calcium ion (Ca2 +) and two Hydroxid ions (2 OH).
This looks as follows: Ca(OH)2 ? Ca2+ + 2 OH-
What does this signify for a reefer?
Calciumhydroxid dissolve itself only badly in water. That's why Calciumhydroxid always stays in the container as white sediment. In the clear solution about that there are calcium ions, Hydroxid ions and of course osmosis water. The pH factor is approx. 12.45. Now this clear solution is the "Kalkwasser".
Kalkwasser is : Ca2+ + OH- in osmosis water
Where is the Kalk now in the “Kalkwasser”? Kalk is a connection of calcium (approx., carbon (C) and oxygen (O)). A carbon (C) is firmly connected with three oxygen (3 O) and proves therefore CO3, a Carbonat. This carbonate increases the carbonate portion e.g. in the aquarium. Calcium (approx.) is now connected with a carbonate (CO3) and results in calcium carbonate or, KALK (lime).
Kalk (lime) is: CaCO3
Kalk and "Kalkwasser"
Now is the question: „Where is the Kalk in the "Kalkwasser"? Yet does not answer, or it is answered? The answer is obvious; it is no Kalk in the “Kalkwasser”. Kalk originates only after some time in the "Kalkwasser". Only if carbon dioxide (CO2) from the air, to the surface of the "Kalkwasser" reaches, this is soaked up and forms then Kalk. This is in "Kalkwasser" not solubly and gives likewise white sediment. For this reason should "Kalkwasser" do not stand open, but in a lockable container, e.g. a can, to be kept. If the "Kalkwasser" (the clear solution) is used, new osmosis water on the remains is given. After a certain time the sediment in the container is exchanged and fresh calcium hydroxide is used, because ever more insoluble lime is present and ever fewer calcium hydroxides.
Calcium hydroxide solution in the aquarium
The clear calcium hydroxide solution, i.e. calcium ions (Ca2+) and hydroxyl ions (OH -) to the sea water aquarium are given, it takes a reaction with the loosened carbon dioxide (CO2) in the water, it develops (simplified represented) calcium hydrogencarbonate (CaHCO3).
Ca2+ + 2 OH- + 2 CO2
The calcium hydrogencarbonate is not stable and disintegrates into an calcium ion (Ca2+) and an hydrogencarbonate ion (HCO3 -)
Ca(HCO3)2 = Ca2+ + 2 HCO3-
Since an alkaline pH value is present, reacts the hydrogencarbonate ion (HCO3 -) with a hydroxyl ion (OH -).
Now also the carbonate portion in the aquarium rises. The rise depends thus before all of the pH value and of the carbon dioxide portion in the aquarium water.
The so-called "Kalkwasser" has nothing to do with Kalk; it consists only of calcium ions and hydroxyd ions. Only if the clear calcium hydroxide solution is given to the aquarium develops at the end carbonate. An accurate controlling of the carbonate portion is hardly possible, since it depends of the carbon dioxide content in the water.
The Reefer thinks usually of very expensive, complex and complicated devices. I would not like to explain a comparison of products, only fundamental principles.
What to heck is a calcium reactor and how he functions? All the same whether built or bought, often one hear problems such as carbonate hardens does not rises, not enough calcium, pH value falls e.t.c.. The Calcium reactor should function according to a simple principle, but it does also? One gives carbonic acid to a container (reactor), filled with a substrate, at the end a solution comes out with...? This is not only too simply represented, but also still wrong. Therefore step by step.
A goal of the Calcium reactor is it, in its inside to divide the substrate into the individual components to thus solve. These arrive then into the sea water aquarium. The Calcium reactor is filled with a substrate, which lime (CaCO3) must contain. Lime dissolves in sour solutions easily, while in alkaline solutions the Kalk is present as white sediment. Since a seawater aquarium has mostly an easily alkaline pH value between 8,0 and 8,4, the substrate does not dissolve. For this reason the pH value must be brought in the reactor into a sour range (smaller 7). This can not happen in the aquarium, but must in the Calcium reactor. In order to lower the pH value in the reactor, becomes carbon dioxide (CO2) as gas (and not carbonic acid!) admitted. The carbon dioxide (CO2) is loosened in the water (H2O). Carbonic acid develops,
This reaction does not change the pH value yet. Carbonic acid is however very unstable and disintegrates simplified into an acid (H+) and into a hydrogencarbonate (HCO3 -),
Now, if the acid (H+) is present, the pH value in the reactor is lowered. If the pH value is low enough, the substrate dissolves slowly. The insoluble Kalk (CaCO3) is converted now simplified by the “acid” (H+) into soluble calcium hydrogencarbonate (Ca(HCO3)2).
The calcium hydrogencarbonate is not stable and disintegrates into an calcium ion (Ca2+) and an hydrogencarbonate ion (HCO3 -),
Ca(HCO3)2 = Ca2+ + 2 HCO3-
Thus calcium ions (Ca2+) and hydrogencarbonate ions (HCO3 -) arrive in the sea water aquarium. Since an alkaline pH value in the sea water aquarium is present, reacts the hydrogencarbonate ion (HCO3 -) with a hydroxyl ion (OH -), which is in great quantities in the aquarium present. Now an carbonate ion (CO32 -) and water (H2O) develop,
Now also the carbonate portion in the aquarium rises.
Dissolution of the substrate
In order to accelerate a dissolving, a high flow rate must be present in the reactor. n to broad reactors (diameter more largely 12 cm / 5 inch) very strong pumps must be used (more than 2,500 litres / 660.gal per hour), in order to receive a high flow rate. The use of fine substrates leads to a strong reduction of the flow rate in the Calcium reactor. The substrate has a larger surface for the acid attack. Is the current however too small, the CO2 vesicles gather in the substrate and prove big CO2 bubbles? If that is the case, hardly substrate can be dissolved. In some reactors even the substrate lift themselves and a large gas bubble become visible.
If one uses now a substrate, which consists of pure lime, then only calcium ions (Ca2+) and Hydogencarbonat ions (HCO3 -) are led in the aquarium. If crushed corals used, then pollutants are set free such as phosphate, aluminum and silicic acid additionally and enrich themselves in the water. It can arrive very much phosphate by crushed corals into the aquarium, better one does without it.
Result Calcium reactor
The Calcium reactor enriches the aquarium water with calcium ions (Ca2+) and Hydogencarbonat ions (HCO3 -). The pH value is raised and stabilized by the addition of hydrogencarbonate. When using shell still further trace elements are brought in. With a Calcium reactor arbitrary KH- and calcium values can be adjusted in the sea water aquarium without problems, contrary to "Kalkwasser", with which one cannot adjust accurate values.
Calcium reactor and "Kalkwasser" operate together
Some sea water aquariums operated with a Calcium reactor and at the same time the refilling water is "Kalkwasser". The KH- and/or calcium values are nevertheless sometimes in the aquarium not sufficient. What can be the reason? Are the devices laid out too small or do play still other different factors a role? As example serves a sea water aquarium with pH 8, a Calcium reactor delivered an calcium ion (Ca2+) and an Hydogencarbonat ion (HCO3 -). The hydrogencarbonate ion is converted fast into an carbonate ion (CO32 -), sees above. The two ions are complete free and to them meet and again lime (CaCO3) form, it lasts for a long time. Now come however from "Kalkwasser" e.g. 100 calcium ions (Ca2+). In the aquarium now are 101 calcium ions (Ca2+) and one carbonate ion (CO32 -). The probability that an calcium ion the carbonate ion finds is now much more possible, and thus lime precipitates many faster. This effect is also observed when “Kalkwasser” by hand directly into the aquarium is given. Then turns the intake for a short time until milk-white color.
By the simultaneous employment of Calcium reactor and "Kalkwasser" the carbonate from the aquarium is precipitated as lime and cannot be taken up by the corals. "Kalkwasser" works against the Calcium reactor. As result is to be said, it should only one of the two possibilities be used. I would prefer the Calcium reactor, with it the calcium can be adjusted in the aquarium very exactly. However also the calcium reactor has a possible negatively factor. The increased CO2 entry by the Calcium reactor can promote algae growth, above all if phosphate and nitrate are present in measurable concentrations.