Can I dose Calcium and Magnesium together?

[shollis2814]

I know Reef Complete has both. The label says there are 155mg Ca and 8 mg of Magnesium in a 5 ml dose. I know you shouldn't dose anything with alkalinity.

I am adding a magnesium supplement and my calcium is just a hair low at 380. My alkalinity is at 11 dKh.

I know Magnesium increase can increase calcium and decrease alkalinity. Am I probably OK to also dose some Calcium with the Magnesium to give it a little boost? Is there a magic ratio in the Reef Complete formula?

I am doing the 15g/80l dosage of the magnesium supplement.

 

[Reab]

The interaction that magnesium(Mg) plays in the chemistry is to keep the calcium(Ca) and alkalinity(Alk) apart. Mg binds to the Alk compound stabilizing it and in turn keeping Ca separate. Mg will not react with Ca so you are fine in dosing them at the same time. If you feel uncertain still, remember your tank has a high turnover rate and the two will eventually come in contact with each other. If you wait 5 minutes between additions the first solution will have already been mixed in to the water column. To be on the save side, you can add one to the overflow and one to the return pump.

 

[Randy Holmes-Farley Verified Community Expert]

I know Reef Complete has both. The label says there are 155mg Ca and 8 mg of Magnesium in a 5 ml dose. I know you shouldn't dose anything with alkalinity.

I am adding a magnesium supplement and my calcium is just a hair low at 380. My alkalinity is at 11 dKh.

I know Magnesium increase can increase calcium and decrease alkalinity. Am I probably OK to also dose some Calcium with the Magnesium to give it a little boost? Is there a magic ratio in the Reef Complete formula?

I am doing the 15g/80l dosage of the magnesium supplement.

You can combine calcium chloride and magnesium chloride for dosing.

You cannot combine calcium supplements with magnesium sulfate outside the tank.

Magnesium does not cause any rise in calcium or any drop in alkalinity.

 

[shollis2814]

You can combine calcium chloride and magnesium chloride for dosing.

You cannot combine calcium supplements with magnesium sulfate outside the tank.

Magnesium does not cause any rise in calcium or any drop in alkalinity.

Thanks! I am seeing, in my day to day testing, the effects of these three things as I try to fine tune. I think and teach in analogies. It helps me to think of Magnesium like a carburetor with alkalinity and calcium being the fuel and the air. Tweaking Magnesium up or down alters the calcium alkalinity ratio, hence the carburetor comparison. For a long time I was chasing calcium up when I should have been tweaking Magnesium.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks! I am seeing, in my day to day testing, the effects of these three things as I try to fine tune. I think and teach in analogies. It helps me to think of Magnesium like a carburetor with alkalinity and calcium being the fuel and the air. Tweaking Magnesium up or down alters the calcium alkalinity ratio, hence the carburetor comparison. For a long time I was chasing calcium up when I should have been tweaking Magnesium.

I don't understand what you mean by the magnesium altering the calcium to alkalinity ratio. It doesn't impact the ratio of the two at all or the relative demand for those two in a way you are likely to be able to detect. It can impact the demand for both proportionally.

 

[shollis2814]

I don't understand what you mean by the magnesium altering the calcium to alkalinity ratio. It doesn't impact the ratio of the two at all or the relative demand for those two in a way you are likely to be able to detect. It can impact the demand for both proportionally.

I am not a chemist, and I trust what you are saying. All I know is that when my calcium was low, and I was trying to raise it by adding calcium, my alkalinity would jump up to 13 every time I approached 400. Two local LFS suggested boosting my magnesium. When I started dosing magnesium, I could add calcium and have alkalinity stay around 11. I probably mis-said something with my analogy, but that is the effect it *seems* to be having.