Magnesium Adjustments

[spsick]

Randy, I need to make 100ppm adjustments to magnesium on new mixed instant ocean. Can you explain the chloride/sulfate differences? Am I to understand a mix with only a little sulfate is better for large additions?

 

[Randy Holmes-Farley Verified Community Expert]

The answer actually depends on the reason for wanting to raise the magnesium and how you are adding calcium and alk to the aquarium.

 

[spsick]

The answer actually depends on the reason for wanting to raise the magnesium and how you are adding calcium and alk to the aquarium.

It’s just to get the low level up to normal on new water. New Instant Ocean coming in at 1230 want to raise it to 1330. On the tank I’m using your 2 part + part C

 

[Randy Holmes-Farley Verified Community Expert]

It’s just to get the low level up to normal on new water. New Instant Ocean coming in at 1230 want to raise it to 1330. On the tank I’m using your 2 part + part C

Ok, then use the 10:1 recipe, mag chloride to magsulfate.

Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

 

[spsick]

Follow up question for you @Randy Holmes-Farley. Does making this adjustment have a meaningful increase to salinity? On their latest salt video BRS said that is does and is actually driving the amount of other elements down as a byproduct. Curious on the actual chemist take on that.

 

[Randy Holmes-Farley Verified Community Expert]

Follow up question for you @Randy Holmes-Farley. Does making this adjustment have a meaningful increase to salinity? On their latest salt video BRS said that is does and is actually driving the amount of other elements down as a byproduct. Curious on the actual chemist take on that.

A 100 ppm boost to magnesium will boost salinity by about 0.3 to 0.4 ppt (say, 35.0 to 35.4 ppt), so yes, the effect is real.