从淡水系统到盐水系统的最大差异之一是更加重视水化学。学习曲线非常陡峭，可以掌握所有不同的化学参数，这可能是许多有抱负的礁石业余爱好者的挫败感。在丰富的石质珊瑚的水族馆中，钙，，，，碱度，，，，and magnesium are important to monitor. This article will focus on magnesium, an important but often overlooked ion in reef chemistry.
What is the role of magnesium in the reef aquarium? First off, it is the third most abundant ion in salt water. The two most abundant ions, for those that are curious, are sodium and chloride. That should come as no surprise, as sodium and chloride make up table salt and give saltwater its characteristic taste.
Magnesium, like most other ions in salt water, is measured in parts per million (ppm). Parts per million is a slightly deceptive sounding unit of measurement. It is a mass ratio rather than an exact count of ions in solution. For example, magnesium represents 1300 ppm while calcium is around 425 ppm. It appears that magnesium is three times more abundant than calcium, but in reality it is much more. Parts per million takes into account the mass of the ions, and it just so happens that calcium is significantly heavier than magnesium. Therefore, magnesium is actually five times more abundant than calcium if you are counting the individual atoms.
镁离子在溶液中带有两个正电荷。钙在溶液中还带有两种正电荷，因此，这两个离子的行为相似，并被我们的珊瑚居民以类似的方式利用不足为奇。当石质珊瑚形成其骨骼时，镁定期取代钙。
镁，钙和碱度的相互作用彼此紧密相关。在我在潮汐花园的一个系统中，我刚刚很难保持钙和碱度。在天然海水中，钙约为425 ppm。测试表明，我们水箱中的钙水平远低于该水平。在325 ppm处，简而言之，比应该击中100 ppm。当我们开始将钙添加到水箱中时，经常发生的是，随着钙的上升水平，我们的碱度下降了。这些离子似乎随着水平的变化而彼此抗争。
当Reefers仅测试钙和碱度时，可以使两种水平与天然盐水相匹配，这可能是非常令人沮丧的舞蹈。这是镁发挥作用的地方。在上面的示例中，镁水平很可能很低。镁通过与碳酸盐离子键合提供缓冲能力。（请记住，碳酸盐硬度是碱度的另一个术语。）由于镁结合了碳酸盐，因此与不存在镁相比，它可以在水中产生更多的碳酸盐。适当的高镁水平允许添加钙，而无需相关的碱度下降。
In summary, we hope this article clears up a little bit the role of magnesium in our water. If you test your water and magnesium is low, there are a few ways to boost it. Most salt mixes these days have a good amount of magnesium already. You could just do more水变化随着时间的流逝，镁水平将上升。
