Corals, calcareous algae and other invertebrates use large amounts of Calcium for the building of their skeletons or shells, which mainly consist of Calcium Carbonate (CaCO3).
Calcium easily precipitates (comes out of solution) as Calcium Carbonate, especially at higher pH values. Because of this, and as a result of continuous usage by invertebrates, this element is quickly used up in the limited volume of the marine aquarium.
A high Calcium level for the reef aquarium in which so many organisms build calcareous structures is essential. A gradual decrease in the concentration of this essential element will result in growth stagnation and degeneration of invertebrates. The Calcium level of natural seawater is approximately 400 ppm.
A level of at least 400 ppm should be maintained in the aquarium, however, for optimal coral growth 450 ppm is even better.
It is recommended to measure the Calcium concentration every week.
Special Note
Tap water always contains Calcium (up to approximately 100 ppm). When you dissolve Red Sea Salt in tap water,the resulting Calcium level will have an optimum value (450 ppm of Calcium). A slight amount of surplus Calcium may even precipitate out, forming Calcium Carbonate.
Users of Reverse Osmosis water, will obtain a slightly lower Calcium level under the same circumstances, since most of the Calcium has been removed by the Reverse Osmosis process. For these aquarists we advise to add Calcium to their R.O. water, for example by putting coral sand, crushed coral or dolomite in their water storage tank, or by using a Calcium additive such as Red Sea’s Reef Success Calcium.
Recommendations
The simplest, but good method of maintaining a high Calcium level is to change the water regularly.
If a Calcium level of 350 ppm or less is detected carry out a 10% water change and test the Calcium again
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