During the last years the reef marine aquariology underwent many changes. Some increasingly better maintenance methods and progress in the aquariology technique enabled the breeding and reproduction of hard corals. This, moreover, made it necessary to provide many lime builders with the essential calcium and hydrogen carbonate ions. For the maintenance of the hard corals, the way was opened with the method of the calcareous water (Lime water or Kalkwasser), which Peter Wilkens made popular during the beginning of the ‘70s. Until 1994 this was actually the only method to provide calcium ions. This technique employs a solution saturated with calcium hydroxide that, with the help of a thin rubber tube is introduced, preferably drop-by-drop, into the aquarium. I found this procedure quite long and not ideal for the invertebrates, because the animals due to the increase in the pH value were subjected to a temporary closing. For this reason searched other ways to provide the invertebrates of a reef aquarium with the necessary calcium and hydrogen carbonate ions. Undoubtedly, the method of the calcareous water has proved to be valid in aquariology since, as previously mentioned, it has paved the way for the maintenance of the hard corals. However, such procedure is limited to two circumstances. The solution saturated with calcium hydroxide, with which the evaporated water is replaced, contains at most 1,7 grams of calcium hydroxide or 900 mg of calcium per litre. In addition, the pH value of the aquarium cannot be excessively increased since that would lead to a precipitation of the calcareous substances. At the end of 1993 I started to employ in the aquarium some very soluble salts of calcium and hydrogen carbonate. This method, which in the meantime bears my name, was made public in 1994, shortly after the publication of a very similar technique by Ernst Pawlowsky (1994) and simultaneously with the calcium reactor by Hebbinghaus (Hebbingghaus, 1994), (Balling, 1994). My method differed from Pawlowsky’s in the disadvantage of a more complicated and less safe manipulation, but it benefitted from the decisive advantage of not altering the ionic balance. In May 1996 I presented an improvement of the “Balling Method” that united a dosage of trace elements (“Trace elements” according to Balling) with the provision of calcium chloride and sodium hydrogen carbonate, enabling an automatic introduction of both the compounds (Balling, 1996). In this context I would like to present the readers with this improved method and expose further experiences.
The method is based on the idea that solutions like calcium chloride and sodium hydrogen carbonate may contain relatively high concentrations of calcium and hydrogen carbonate ions needed for the management of a reef aquarium. While these two salts, in my first publication of 1994, were still united in a sole solution, implying the real risk of their reaction already in this context, the article of Mai dated 1996 presented the possibility of a separated dosage. The solutions are determined in such a way that 1 Mol of calcium chloride corresponds to two Mols of sodium hydrogen carbonate, each dosed in a solution of two litres. The zooxanthellae of the corals provided with symbiotic algae shift this balance towards the right through the consumption of carbon dioxide, leading to the formation of calcium (CaCO3), in the form of the calcareous skeleton of the corals.
Sodium chloride-free marine salt
However, of the two administered salts, calcium chloride and hydrogen carbonate, the chloride and sodium ions still remain in aquarium. This happens because they are neither consumed nor subjected to precipitation. The sodium chloride, though, is nothing but cooking salt and in other words an important part (around 70%) of the composition of a marine salt mixture. Nevertheless, this way would lead to an excess of salt (sodium chloride) in the water of the aquarium. To prevent this from happening it is necessary to use a sodium chloride-free mixture of marine salt (e.g. “Tropic Marin Pro Special Mineral”, formerly “Tropic Marine Export”), to compensate the increase in the sodium chloride of the aquarium, since in this way all the remaining elements of a saline mixture are also provided to the aquarium water. What remains of one Mole of calcium chloride and two Mols of sodium hydrogen carbonate are now two Mols or 117 grams of sodium chloride, which must be compensated through 50 grams of a sodium chloride-free marine salt. A marine salt of this kind is not easily soluble, since it contains calcium, sulphates, carbonates and other salts that react with one another. For this reason, it is more practical to mix for the change of water the quantity calculated with a normal marine salt. In this way, the 50 grams of sodium chloride-free marine salt replace the 167 grams of a common product. The increase in density through the addition of salts providing calcium is automatically compensated. After having made, after a short time, some changes to this method, enriching it with other compounds such as magnesium chloride, Ernst Pawlowsky continued to use calcium chloride and sodium hydrogen carbonate in the way exposed above, detecting an increase in the carbonate hardness. This fact did not seem to have an explanation. I think that it is possible to get closer to the solution by wondering why the permanence of the hydrogen carbonate ions in solution seems longer than that of the calcium ions. Probably, a sufficient quantity of calcium and magnesium ions in the form of phosphates, ammonium phosphates and sulphates that precipitate explain the observed increase in the alkalinity.
What is a MOL?
The concept Mol, as well as the metre or the second, is one of the seven International basic unities. It is a measure related to the quantity of a given substance, with which any chemical element (number of particles) can be expressed with precision. With the help of the molar mass of the elements, it is possible to easily determine that of the compounds too. This molar mass is also important to determine the quantity of substances transformed in a chemical reaction. The molar mass of sodium hydrogen carbonate (NaHCO3), for example, corresponds to 84,01 grams. One Mol of a substance contains 6,0221367 x 1023 particles (molecules, atoms, ions) of the same. The molar mass M also results as important, determining the balancing of one Mol of a substance. For instance: the chemical formula of the cooking salt is NaCl. If we unite, in simple terms, 100g of sodium and 100g of chlorine, they are not enough to reach 200g of NaCl. In this case an atom of sodium reacts with one of chlorine. With this example the 23 g of sodium and the 35,5 g of chlorine each represent one Mol, since the number of atoms is the same for both the substances. Therefore a reaction should be caused between 23 g of sodium and 35,5 g of NaCl. In the example of 100 g, in fact, we had too few atoms of chlorine (4,32 mol Na and 2,82 mol Cl). The maximum result would be 2,82 mol that is 165 g of NaCl. So, the sodium would be excessively available (35 g meaning 1,52 mol). Adapting the whole thing to a reef aquarium, the ionic balancing would be significantly altered, since an excess of a determined substance would be available.
From 14 grams of chloride dihydrate and 168 grams of sodium hydrogen carbonate, 100 grams of calcium carbonate, 44 grams of carbon dioxide, 117 grams of sodium chloride and 54 grams of water are obtained.
Ca2+ + 2 HCO3- € CaCO3 + CO2 + H2O