High Calcium, Low Magnesium?

[ENDUexe]

Looking for a bit of guidance here. My last two calcium and magnesium tests have left me scratching my head a little.

I've been using Aqua Medic Reef Salt and mixing it to an SG of 1.025, based on my LFS's initial recommendation. For the past couple of weeks, I've been mixing my water changes to 35 ppt instead, and I plan on bringing the tank up to this new salinity over the next couple of months.

Aqua Medic says the salt should give 420 calcium and 1200 magnesium at 35 ppt, but I'm seeing 470 calcium and 1140–1170 magnesium, using salifert test kits. The magnesium numbers make sense given my slightly lower salinity, but I'm not sure what to make of the calcium.
If anyone could shed some insight as to why I might be seeing the elevated calcium numbers, that would be greatly appreciated.

I'm currently only dosing sodium bicarbonate, but I'd like to switch to All For Reef in the near future. I'm just concerned my calcium will run away on me. Should I just start dosing magnesium alongside alk rather than making the switch?

 

[Randy Holmes-Farley Verified Community Expert]

Those don’t seem too far off, especially with the low reliability of magnesium testing.

Calcium is fine higher than yours is now (at least up to 550 ppm, IMO) so I would not worry too much about it rising.

 

[ENDUexe]

Those don’t seem too far off, especially with the low reliability of magnesium testing.

Calcium is fine higher than yours is now (at least up to 550 ppm, IMO) so I would not worry too much about it rising.

Thanks.

Do you think it would be beneficial to slowly dose my mag numbers up to around 1300 prior to starting A4R? Maybe even dose the water change mix up prior to the WC?

 

[Euphylliaphyle]

Thanks.

Do you think it would be beneficial to slowly dose my mag numbers up to around 1300 prior to starting A4R? Maybe even dose the water change mix up prior to the WC?

I would not worry about it. This is a game of "close enough" due to measurement error. If it is indeed a tad low, AFR and water changes will slowly bring it in line.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks.

Do you think it would be beneficial to slowly dose my mag numbers up to around 1300 prior to starting A4R? Maybe even dose the water change mix up prior to the WC?

I think it may be higher than the test indicates.

That said, Is there a reason to stick with this salt?

 

[ENDUexe]

Thanks.

Do you think it would be beneficial to slowly dose my mag numbers up to around 1300 prior to starting A4R? Maybe even dose the water change mix up prior to the WC?

I would not worry about it. This is a game of "close enough" due to measurement error. If it is indeed a tad low, AFR and water changes will slowly bring it in line.

The bucket only claims 1200 at 35ppt so that may not be enough. I’ll test the next batch to see just how close my measurements get me.

 

[ENDUexe]

Thanks.

Do you think it would be beneficial to slowly dose my mag numbers up to around 1300 prior to starting A4R? Maybe even dose the water change mix up prior to the WC?

I think it may be higher than the test indicates.

That said, Is there a reason to stick with this salt?

Nothing other than financial investment. I have 20 kilo bucket that I’d prefer to use and given the size of my system, it will likely last a while.

 

[Randy Holmes-Farley Verified Community Expert]

Nothing other than financial investment. I have 20 kilo bucket that I’d prefer to use and given the size of my system, it will likely last a while.

Ok, dosing some magnesium to that one seems appropriate since it does not measure up to seawater even by its own specifications.