Dosing magnesium

[Myka]

I use Fauna Marin Magnesium chloride. I add 2 cups to my 15-gallon waterchange tub along with 1 tbsp epsom salt (Magnesium sulfate) using H2Ocean salt. The "perfect" ratio according to Randy Holmes-Farley (I think it was him) is 8.5:1. You do not want to use epsom salt as the primary source because there will be too much sulfate in the tank. It takes a lot of powdered magnesium product to raise magnesium, meaning there is a lot of chloride (or sulfate) being added. Adding the product this way, I do not have to dose magnesium otherwise.

[lastlight]

Yeah I use the mag chloride and sulfate mix. Or will someday lol. There was a time when I did have to occasionally dose it.

[reefermadness]

My guess is the new salt mix is lower in magnesium. Personally I would be happy with 1240ppm and leave it be. If it lowers to 1200ppm you might want to add 100ppm and you can safely do that with epsom salt USP from any pharmacy. Use the reef chemistry calculator to figure out how much, add it to some RO/DI and split the dose into two days.

[Myka]

I missed answering the "and why?" part of your question... The way I do it is easy, it works, and I don't forget it. I add potassium in the same manner.

[Delphinus]

As Myka stated it takes a lot of Magnesium to raise a Mg reading in a tank, so don't be shocked.

I just top up my SW, I know how to much to add to make my ingoing water 1500Mg and that seems to combat the Mg drain just fine. I was using Mag sulfate and Mag chloride from Eli and use the same dosing instructions as per BRS..