Quote:
Originally posted by JB NY
Magnesium.
In all honesty I don't understand magnesium as well as the other two parameters. I know that corals do take in magnesium so it is needed on that level.
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The primary benefit of Mg is that it allow calcium and bicarbonate levels in the water to exist at supersaturated levels. In laymen's terms, having high Mg allows you to maintain higher Ca/Alk.
Because Ca and bicarbonate are supersaturated, they are always ready to fall out of solution. This is the abiotic precipitation that every talks about on heaters, pumps, and solid surfaces. As calcium carbonate forms on these surfaces, Mg is also able to bond with it. By doing so, Mg blocks Ca and bicarbonate from being able to attach, significantly slowing the rate of precipitation. If you let Mg drop, you have to pour in more and more Ca and Alk supplements, and precipitation becomes more and more of a factor.
I don't think corals deliberately use (or require) Mg, it's more of an incidental pick-up while building their skeletons. But, maintaining Mg levels is necessary to hold Ca and Alk levels where you want them.