Starting point for Alk/Ca Dosing

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by turbo2oh, Mar 8, 2018.

  1. turbo2oh

    turbo2oh Member

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    So I have a 60g cube with a 20x20x13 sump. I'm estimating around ~60g total volume. I'm trying to determine a good starting point for daily Alk/Ca dosing assume both are added equally. I'm using the BRS Alk/Ca mix it yourself stuff (not the brand new package version).

    Here are my Alk readings right after a water change
    3/5 - 8.1 (day after water change)
    3/6 - 8
    3/7 - 7.8
    3/8 - 7.7

    It seems to deplete at ~.1dkh/day. With this as a starting point what should I be dosing in Alk/Ca per day assuming I want to keep it at 8.1?
     
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  2. AdamNC

    AdamNC Lawnmower Blenny says nom nom R2R Supporter R2R Excellence Award R2R Secret Santa Build Thread Contributor

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    cracker and turbo2oh like this.
  3. 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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    Use this calculator and Randy's Recipe 1 to determine the daily dose to give 0.1 dKH per day. Dose both parts equally.

    http://reef.diesyst.com/chemcalc/chem_calc3.html
     
  4. turbo2oh

    turbo2oh Member

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    Thanks! I see what my dosage should be to move my Alk 0.1dkh/day (4.2 ml; 0.1 fl oz; 0.8 tsp). I'm still not clear on how to determine how much Calcium to add per day. It shows me what the balanced Calcium level is for the given Alk, but not how much to dose. Do I need to log it across several days as well and calculate it separately?
     
  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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    If you are adding 0.1 dKH of alkalinity, then add about 0.7 ppm of calcium each day, which equalizes the demand for calcium carbonate (2.8 dKH of alk for each 18-20 ppm of calcium).

    FWIW, with demand so low, it is actually hard to know exactly what is causing that demand (there are a variety of minor processes), and it may not be formation of calcium carbonate at all, but it is a good starting point.
     
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  6. turbo2oh

    turbo2oh Member

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    Ok, great thanks. Regarding your FWIW, are you saying that I may not have to be dosing Ca at all? I'm not sure what to take away from your statement :)
     
  7. 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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    No, I'm not suggesting that. I'm suggesting it might have been fixing a low calcium situation, but that much calcium demand will not continue for long if there is no similar amount of alk demand (except as water changes might cause it with a low calcium, high alk mix, like normal IO).
     
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