Magnesium from a Ca Reactor?

[Poseidon]

What options are there to add Magnesium to your tank, using a Ca Reactor? I have a few pounds of SeaChem's gray coast in there now, along with 200 pounds or so in my tank. According to SeaChem, this sand has:

Elemental Concentrations in Gray Coast™
Calcium
197,500

Cobalt
4

Iron
2876

Potassium
417

Magnesium
115400

Manganese
43

Molybdenum
6

Strontium
63

Vanadium
7

Zinc
23

All in PPM I believe.... This is a CALCITE gravel though, so I know that it won't dissolve in the tank, where the pH is 8.3 or so, but I thought I would be able to get at some of that magnesium at a pH of 6.5! Maybe I need to add more to the reactor?

[Samper]

I tried to use oolitic sand in my reactor and wasn't getting much of a result. It would pack in too tightly and my spray bar wasn't able to deliver CO2 except for through the exposed holes in the spray bar. These holes were above the level of the sand in the chamber and didn't accomplish anything. I'm now using Koralith media because I got a steal of a deal on it. It works pretty well coupled with the limewater reactor but I still find myself dosing Mg monthly. The next time I order I'm going to try ARM.

I may be wrong but doesn't Mg carbonate dissolve at a lower pH than aragonite? I seem to remember something about people driving the pH lower in their reactors and they were using dolomite and a reactor media together.

[Samper]

This article mentions dolomite and some other alternatives.

Chemistry and the Aquarium

[Papa Doug]

Mine use to stay at 1250ppm, when using ARM. Currently, as I dont run a reactor anymore, I add magnesium and calcium,{similar to Randys recipe}, to my IO salt mix.