Alk and kh test help

Discussion in 'Water Chemistry' started by Peredhil, Sep 29, 2008.

  1. Peredhil

    Peredhil Giant Squid

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    I've been using an Alkalinity test from Aquarium International. It's the first drop -> blue, count drops until it's yellow. Including that first drop, it takes 7. It tells me to divide by 2 - so the unit is 3.5. This number doesn't make sense to me.

    I got in my API Reef test kit and this has a Carbonate Hardness (kh) test. It's basically the same thing. Only with this test, it takes 10 drops to go from blue -> yellow. According to its chart, this means I have 179 as my score.

    I did both tests, back to back, twice. Same results as stated above.

    So I've got a couple questions - so far, this is the test I understand the least.

    1. I've read that alk and kh are interchangeable. Is this true? If it is, I will stop with the alk test and rely on the API kh test.

    2. The API kh test says that ideally it should take anywhere from 8-12 drops. Do you agree 3reefers? Giving me a score of 179.

    As a matter of FYI, I will list all scores from my last testing round (yesterday). But I'm only asking for info on the above. (BTW - tank is a few years old, but moved to my house 8/15 (same water, etc.))

    Temp 79 <consistent>
    SG 1.027 <consistent>
    Ca 400 <mostly consistent>
    PH 8.4 <I'm getting better at deciphering the colors on this one>

    Ammonia, Nitrite both 0 <consistent since 9/12>
    Nitrate 15 <was at 20 since 8/23, seems I'm ending a cycle>
    Phosphate .5 <first time to run> that's point five.

    And of course

    Alk 7 drops or 3.5 after conversion - if I'm converting correctly? But it's been 7 drops since 8/25 when I first got this test.

    kh 10 drops/179. First time to run it.
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  3. PharmrJohn

    PharmrJohn Giant Squid

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    If it is like mine, then you multiply the 3.5 by 2.8 to get the dKH to get 9.8. The 179 sounds like ppm. In order to convert that to dKH, you divide by 50 then multiply by 2.8.

    179/50=3.58
    3.58x2.8=10.02 dKH

    Just off the top of my head. But it looks right given the numbers you supplied using both tests. And yes, they are interchangable. You can do a series of multiplications and/or divisions to convert from one to the other. They indicate the same thing in the end, just from different angles.
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  4. ALW

    ALW Sea Dragon

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    Nice work PharmR.
  5. ermano

    ermano Zoanthid

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    i use the API kH test too and it states that however many drops it takes then thats what your dKH is. So say it takes 11 drops to turn it from blue to yellow, then you have 11dKH. Like PharmrJohn said, the conversions go like this...


    1 meq/l = 2.8 dKH = 50 ppm CaCO3(Calcium Carbonate)
  6. Peredhil

    Peredhil Giant Squid

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    Thanks! Just the explanation I was looking for pharmr
  7. PharmrJohn

    PharmrJohn Giant Squid

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    No problem man.