The Balling Method Addition of hydrogen carbonate and calcium in reef aquaria – Part 2

Addition of magnesium

However, this increase in the carbonate hardness results as problematic, since values over 8°dKH make it difficult to realise a sufficient calcium content of around 420 milligrams per litre (mg/l), needed for a good growth of the corals. It must be taken into account that the natural carbonate hardness is approximately just 6,5 °dKH! Another slow shift of the ionic balance occurs with the constant decrease of the magnesium content, by introducing calcium chloride and sodium hydrogen carbonate. The attempt to increase the magnesium content in the aquarium with the “Balling Method” does not make sense, in my opinion, since an increase of just 4,3 mg/l of magnesium forcibly provides a growth of the carbonate hardness by one degree according to the German scale of hardness (°dKH). This means that an increase in the 1100 mg/l magnesium content of the aquarium water by 200 mg/l, towards a natural value of 1300 mg/l, implies a surge of the carbonate hardness by 46° dKH! For this reason, I think that the separated provision of magnesium salts without the increase of the buffer substance makes more sense. Through the addition of these salts from the mineral acids, the carbonate hardness is reduced slowly but persistently and the calcium content stabilises. The calcium chloride, on the contrary, has a less persistent effect on the decrease of the carbonate hardness. For this purpose, I want make a further change to the “Balling Method” to obtain an additional increase up to ten per cent of the magnesium weight (a proposal by Pawlosky). Basically, this would imply a mixture between the solution of calcium chloride dihydrate and magnesium chloride hexahydrate (see the table for the quantity). However, it is absolutely unnecessary to respect the ratio 1:10, because the consumption of the single elements with a different occupation of the aquarium may vary. Those who had a minimum knowledge in chemistry and the effects of salts, should rather try to determine the salts between one another in such a way to measure, with a 420 mg/l content of calcium and a 1.300 mg/l one of magnesium, a carbonate hardness of around 7 °dKH. In this way the dosage of important elements like calcium and magnesium, as well as that of hydrogen carbonates, is ensured.


Hard corals like this brain coral build a skeleton of aragonite, a form of calcium carbonate.

Addition of magnesium to the calcium chloride

34 grams of magnesium chloride hexahydrate are mixed with the solution of 147 grams of calcium chloride dihydrate. This ratio may be varied over time, reaching in the aquarium water up to the following values: calcium content 420 mg/l, magnesium content 1.300 mg/l, carbonate hardness 7 °dKH.

Part 1