Rocks leaching Magnesium?

[Enderg60]

I have a tank im setting up as a coral QT system which I started with some dry rock. Its all going well but for some reason my magnesium keeps rising on its own. Using Reef crystals salt which is usually in the 1450 range when mixed after a 100% water change the mag reads right at 1450. After a week its over 1500, after a month its over 1800. I do 100% change again and it starts climbing again.

The only things in the tank are about 10 lbs of rock, 4 cups of matrix in sump and 1 cup of carbon, changed every 2 weeks. Im very confused.

 

[Randy Holmes-Farley Verified Community Expert]

I'm guessing test issues unless it is some very unusual rock. No normal reef rock can leach magnesium without alk going through the roof.

 

[Enderg60]

Ive tested with salifert, and red sea manually, and red sea in a mastertronic. All within 50ppm of each other, and the trend repeats after each water change.

Unless a dosing pump (which is unplugged BTW) is malfunctioning I cant imagine what could be causing this.

 

[Randy Holmes-Farley Verified Community Expert]

Ive tested with salifert, and red sea manually, and red sea in a mastertronic. All within 50ppm of each other, and the trend repeats after each water change.

Unless a dosing pump (which is unplugged BTW) is malfunctioning I cant imagine what could be causing this.

Salinity going up?

 

[Randy Holmes-Farley Verified Community Expert]

What rock material?

 

[jda]

Did you use dolomite and have low pH in the tank where it is dissolving?

 

[stoney7713]

I don't mean to resurrect an old thread but I am searching for answers too. Did you ever figure anything out on this?

I'm actually experiencing the same thing. Magnesium climbs yet I am not dosing anything except BRS kalk. It was rising even before that.

I started with Marco dry rock and CaribSea dry sand, bacteria in a bottle, seeded with 15# of live rock.

Using IO Reef Crystals, Mg is 1350-1400 on new batches yet my tank is peaking out over 1600 closer to 1800 a few tests ago.

Calcium staying around 450 and alkalinity around 9.

Could it be from pumps or other equipment?

 

[Randy Holmes-Farley Verified Community Expert]

Could it be from pumps or other equipment?

No, there's just no normal in-tank source for substantial magnesium. It might be top off water, an additive of some sort, or test error.

You used the same kit side by side with new salt water and the tank water at the same salinity?