What might be raising my mag levels?

[HawkeyeDJ]

I have a 24g AIO cube. I do not dose anything. I buy my saltwater from my lfs. It is Red Sea. The water from the lfs tests at 1400 magnesium, but the water in the tank tests at 1600. I typically do a 20% (5 gallons) weekly.

I only have one sps, a small montipora cap. Other corals include GSP, toadstool leather, some zoas, and a couple of hammers.

Any ideas what might be raising my mag levels? And what might be the consequences?

 

[Garf]

I have a 24g AIO cube. I do not dose anything. I buy my saltwater from my lfs. It is Red Sea. The water from the lfs tests at 1400 magnesium, but the water in the tank tests at 1600.

I only have one sps, a small montipora cap. Other corals include GSP, toadstool leather, some zoas, and a couple of hammers.

Any ideas what might be raising my mag levels? And what might be the consequences?

Increasing salinity would do it.

 

[HawkeyeDJ]

Increasing salinity would do it.

My salinity is very stable at 1.024-25 and has been for many months.

 

[bushdoc]

Do you personally do testing of your tank water and LFS water? If so what tests are you using. Hobby Mg tests kits are prone to errors and inaccuracies.

 

[Garf]

My salinity is very stable at 1.024-25 and has been for many months.

I’m assuming your chosen method of checking salinity is calibrated properly so I think the only other possibility I can think of is test error. The reproducibility of results with magnesium tests are a little problematic sometimes. How do you calibrate your salinity measurements?

 

[HawkeyeDJ]

Do you personally do testing of your tank water and LFS water? If so what tests are you using. Hobby Mg tests kits are prone to errors and inaccuracies.

Yes, I do my own testing. For mag I use Red Sea. Sometimes I have repeated tests just to be sure and they are always relatively close. The tank always tests higher than the lfs saltwater. I've even had the lfs test my tank water and they get the same high 1600 as I do.

 

[HawkeyeDJ]

I’m assuming your chosen method of checking salinity is calibrated properly so I think the only other possibility I can think of is test error. The reproducibility of results with magnesium tests are a little problematic sometimes. How do you calibrate your salinity measurements?

I use a refractometer ATC and I calibrate it with calibration fluid 35ppm every week when I run my tests.

 

[Randy Holmes-Farley Verified Community Expert]

Magnesium never rises unless you dose it, and test error and or salinity changes is a best first guess for nearly every magnesium "problem".

The new salt water at 1400 ppm is tested by you with the same kit? What is the salinity of that new salt water?

FWIW, it is my impression that the Red Sea magnesium kit is more prone than other mag kits to problems.

 

[HawkeyeDJ]

Magnesium never rises unless you dose it, and test error and or salinity changes is a best first gumy first assumption was operator error.ess for nearly every magnesium "problem".

The new salt water at 1400 ppm is tested by you with the same kit? What is the salinity of that new salt water?

FWIW, it is my impression that the Red Sea magnesium kit is more prone than other mag kits to problems.

Salinity of the new saltwater (Red Sea Coral Pro) is always 1.024-25. I check it after I bring it to tank temperature and before I put it in the tank.

When the mag levels were first tested high, my first assumption was operator error, so I ran the test again paying particular attention to timing and measurements. When came back high again, I ran the test on the new saltwater and it came back at 1400, within 10 ppm of the claim on the bucket.

 

[Randy Holmes-Farley Verified Community Expert]

Salinity of the new saltwater (Red Sea Coral Pro) is always 1.024-25. I check it after I bring it to tank temperature and before I put it in the tank.

When the mag levels were first tested high, my first assumption was operator error, so I ran the test again paying particular attention to timing and measurements. When came back high again, I ran the test on the new saltwater and it came back at 1400, within 10 ppm of the claim on the bucket.

FWIW, the change from sg = 1.024 to sg = 1.025 will boost magnesium from 1400 ppm to 1460 ppm, and the range of actual valuss (sg = 1.0235 to 1.0254) to get measurements in that observed range could be even higher.

 

[HawkeyeDJ]

FWIW, the change from sg = 1.024 to sg = 1.025 will boost magnesium from 1400 ppm to 1460 ppm, and the range of actual valuss (sg = 1.0235 to 1.0254) to get measurements in that observed range could be even higher.

Is the reverse also true? If I were to lower my sg down to 1.023 will it lower my mag?

 

[Randy Holmes-Farley Verified Community Expert]

Is the reverse also true? If I were to lower my sg down to 1.023 will it lower my mag?

Yes, exactly the same change in reverse.