Magnesium low in reef tank.

Discussion in 'Reef Aquarium Discussion' started by Jeremy Lain, Feb 8, 2018.

  1. Jeremy Lain

    Jeremy Lain Member

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    Hello, magnesium low in reef tank. Test says 1160 ppm. What to do to bring it up?
     
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  2. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    What kit and what salt mix and salinity?
     
  3. Jeremy Lain

    Jeremy Lain Member

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    I am using an red sea reef foundation pro test kit for testing magnesium and an api test kit for all the other water perameters. I am going to attach a picture of my water perameters. I am using instant ocean sea salt. SmartSelectImage_2018-02-09-09-49-41.png

    The only way I could keep calcium and dkh on the right levels was to bring my salinity down to 1.019. I have read that it needs to be higher but it's not working for me with the peraeters needed.
     
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  4. timnem70

    timnem70 Active Member

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    Thats because your mag is so low. Bring it up slowly by using a magnesium supplement, restest the pther two parameters. They should also come up. Instant ocean has lower mag then some others. Reef crystals has an elevated magnesium number. Get your mag up amd the other two are easier to keep at stable levels. Get you SG up to 35ppm slowly now as well. Over a few days.
     
  5. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    There are a number of possible inconsistencies here: salinity measurement seems like it may be off, low salinity, and a possibly faulty magnesium kit.
    Lowering salinity below normal is not the way to bring a parameter (other than salinity) into line because it drops everything.

    That said, I doubt the salinity is accurate if calcium and magnesium are still that high. They would be much lower with IO at that salinity.

    The salinity is the reason you magnesium is too low (well, one reason, anyway). That kit is also faulty in many peoples hands.

    1160 ppm at a sg of 1.019 will have a magnesium level of 1611 ppm at 35 ppt (sg = 1.0264).
     
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  6. A Toadstool Leather

    A Toadstool Leather Well-Known Member

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    there are supplements you can use to help bring it up. Good magnesium levels make it easier to keep ca up for the most part.
     
  7. Stigigemla

    Stigigemla Active Member

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    I think your salinity meter is way off. In 1.019 I doubt your corals will survive in such a low sailinity.
    Testing procedure for Reef tanks:
    1. Temperature
    2. Salinity
    3. kH
    4. Calcium and Magnesium

    So please take a sample of your water to a reefer in your neighbourhood and test your salinity first.
     
  8. Reef Jeff

    Reef Jeff Active Member

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    Agree with all other posters. Salinity is a combination of all components in the water including calcium, magnesium, strontium, etc, etc. Low salinity means lower values for all the above. Randy makes a good point that if salinity is truly 1.019 then calcium would typically be lower so I suspect testing error is playing out here too. The API Calcium test kit is not very accurate compared to other quality tests.

    Verify salinity first. Then get it up to a proper level slowly so as to not stress your livestock, then retest magnesium. I would NOT add magnesium supplements until you do the above. I suspect your magnesium level is okay as is.
     
    Last edited: Feb 10, 2018
  9. Jeremy Lain

    Jeremy Lain Member

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    Can you help me understand how you got this calculation? "1160 ppm at a sg of 1.019 will have a magnesium level of 1611 ppm at 35 ppt (sg = 1.0264)"? Is there some way they are connected together to equal certain levels? I mean like if one is low are the others affected? The Calcium, DKH, Magnesium, and Possibly PH?
     
  10. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    When you raise salinity by allowing evaporating or adding salt mix, you boost everything in the water (not pH, it isn't controlled that way).

    Concentrations are about linear with the specific gravity (ignoring the leading 1) or the salinity in ppt.

    So, for example, if magnesium is at 1160 ppm at a specific gravity of 1.019 and you allow the water to evaporate down to a specific gravity of 1.0264, the magnesium will rise by a factor of 26.4/19 (the values from the specific gravity change) = 1.39.

    So 1.39 x 1160 = 1612 ppm

    The answer is similar if you top off with salt water to replace evaporation and let the salinity rise in the tank. :)
     
  11. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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  12. Reefsmoker

    Reefsmoker Member

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    Years ago i was sure i was having a Ca problem the test kit i was using ended up being expired like a year, i think i bought it expired and never noticed. Double check kit? Maybe a bad batch of salt mix idk.
     
  13. Jeremy Lain

    Jeremy Lain Member

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    My water keeps evaporating. Do you think this might be happening because the wrong parameters are in the tank,(Calcium, DKH, Magnesium)?
     
  14. beaslbob

    beaslbob Valuable Member

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