This is one of my favorite topics... and relates to dosing Magnesium along with DIY 2 and 3 part systems.
Think of water chemistry as a long bar graph. On the left we have Sodium and Chloride, moving to the right we have Sulfate, Magnesium, Calcium, Potassium... and at the far right you will see elements like Iodine with a concentration around .10ppm.
This is what natural seawater looks like.
Ever wonder what happens if you mix seawater the wrong way? Maybe with more Sulfate than Magnesium? Or too much Potassium compared to Sodium?
Stuff will die.
Over millions of years sea life has adapted to the current composition of seawater.
So what happens when you take happy normal seawater and start dosing Magnesium (Magnesium Chloride)??
You're adding Magnesium and Chloride to the water. So look back at that bar graph. All of a sudden the Magnesium and Chloride bars are a little taller. Well, the corals use some of the Magnesium as part of Calcification so the Magnesium bar will shrink back down to normal size. But what happens to the Chloride? Is it used up by corals or bacteria or clams? No. The Chloride stays in an elevated status. What happens the next week when you dose more Magnesium Chloride? The Magnesium bar and the Chloride bar rise again.
So what's the big deal?
The water in your aquarium is no longer like natural seawater. Natural seawater has normal ratios between the components (elements). The salinity may be higher or lower in different places but the ratios, element to element are fairly stable and consistent (other than areas affected by effluent perhaps)
So why did someone come up with the idea of adding Magnesium Sulfate along with Magnesium Chloride? It is a little better to raise the Magnesium, Chloride and Sulfate bars simultaneously so at least the Chloride and Sulfate are still in a proper ratio.
This brings up the question about 2 or 3 part Calcium and Alkalinity dosing...
As frequently as you add Calcium Chloride, Sodium Bicarbonate (or Carbonate), Magnesium Chloride and Magnesium Sulfate to your system go back to the bar graph.
The most abundant elements,Chloride, Sodium, Sulfate and Magnesium will remain in approximate balance. But the other elements (several dozen of them) will be "unbalanced" with the "big 4".
This is why "Balanced Ion" 2-Part products like Warner Marine C-MAX and ESV B-Ionic exist. A truly balanced 2-Part not only adds Calcium and Alkalinity... but also adds just enough of the other elements, major AND minor to keep that bar graph looking like natural sea water.
Are water changes effective at fixing the ratio of elements in a system? Not really. If you start with unbalanced elements, out of ratio... water changes don't significantly correct the situation unless it's a very large water change.
Thanks.
