Magnesium demand rising rapidly?

[saltyhog]

I usually run my Mg+ at 1400 and dose manually if it falls to around 1350. Usually I only have to dose every 6-8 weeks if not longer. Recently the demand has increased greatly. So much that I had to dose again today after only 3 weeks.

My tank is recovering from a major screw up on my part. We went on vacation the first week of Sept and in all the flurry of preparation I forgot to fill my dosing containers before I left. Worse I didn't realize my mistake which could have been easily corrected with a call to my tank sitter. When I got home alkalinity had fallen from around 8.9 to 5.0! I lost several colonies of SPS I had been keeping since my tank was young (almost 3 years). Some other colonies survived with large amounts of tissue loss but recently they've been coming back strong. I've also added several SPS frags including a monit cap that's growing like crazy. My alk/calcium consumption has gone up by about 50%. This seems out of proportion to the magnesium.

Is there anything negative that would increase Mg+ consumption like that?

 

[Cory]

Wow sorry about that mistake you made.

Im not sure if low alk would effect magnesium depletion.

There are some animals that use excessive magnesium, so if you have them growing it may be why.

It may also be a testing error.

 

[Tahoe61]

Growth of coralline algae can contribute to increased consumption. A value of 1350 is fine and in the range of normal salt water. If you're not dropping below 1250 I would not be too concerned. Your tanks consumption rate has increased or it's a testing error, no harm no foul.

Sorry to hear of your sps loss, that sucks.

 

[saltyhog]

Thanks guys, the SPS loss was my own fault. Next time I leave I will have a check list made out and completed before I leave.

I wasn't worried about my levels as I never let them get low. Just curious as to why it would change after almost three years of stability. Hadn't thought about coralline and it is growing rapidly as my tuxedo urchin keeps eating it and providing new space for it to grow in to, LOL.

I don't think it's a testing issue (retested twice and got the exact same number all 3 times) but I'll get another test kit since it's almost time to anyway. That should affirm or disprove that possibility.

 

[biom]

I don't think it's a testing issue (retested twice and got the exact same number all 3 times) but I'll get another test kit since it's almost time to anyway. That should affirm or disprove that possibility.

Retest with new test kit, old tests read lower Mg. https://www.reef2reef.com/threads/magnesium-depletion-after-soda-ash-sodium-carbonate-dosing.230495/

 

[Randy Holmes-Farley Verified Community Expert]

I'm not sure how much you say magnesium consumption increased, but I agree that you should worry about testing error.

Magneisum consumption will, at its greatest, be a bit over 1/10th of the calcium consumption (in ppm). Coralline can give that sort of ratio.

So for magnesium to drop 100 ppm, calcium would have to decline by almost 1000 ppm.

Of course, if you are supplementing calcium, it won't drop, but you'd need to add that much to get the magnesium to drop 100 ppm.

If your apparent ratio of consumption involves a lot more magnesium than that, relative to calcium,. then it is either testing error, or an issue from water changes changing the levels.

I discuss magnesium, including showing data for the magnesium percentage in coral skeletons here:

Aquarium Chemistry: Magnesium In Reef Aquaria ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2003/10/chemistry

magnesium levels range from 0.05% by weight magnesium to 4.4% by weight.

Comparatively, calcium ranges from about 40% down to 32% by weight.

 

[saltyhog]

My Calcium and alkalinity demand has risen in recent weeks by about 50-60 percent. I have recently changed salt mixes from HW Reefer to plain IO which has a little less Mg. Maybe it is proprtional to my calcium/alkalinty increase all things considered. Will find out when my new test kit gets here.