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Kh/ph/co2

Discussion in 'Are you new to aquatic plants? Start here' started by ronj, Jun 5, 2007.

  1. ronj

    ronj Junior Poster

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    Just about done cycling a new tank. My Salifert KH test kit shows me a reading of
    .6 dkh. I've adjusted CO2 to about 3 bubbles per sec to achieve a PH reading of
    5.8-5.9 (pinpoint monitor) which according to Chuck Gadd, gives me a CO2 level between 20 and 30 ppm. Is this PH too low for average community fish? KH reading from tap water is 1dkh. Which parameter should I be focusing on-KH or CO2? My gut feeling is to leave things alone since plants are growing like mad. Just not sure if I should try to raise KH in order to raise PH. Trying to get an understanding of this relationship. Appreciate any help.
     
  2. VaughnH

    VaughnH Lifetime Charter Member
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    The relationship of ppm of CO2 to KH and pH for water that contains no other source of alkalinity but carbonates and no other source of acidity but CO2 is a mathematical equation of the form:
    CO2 is proportional to KH divided by 10 to the power of the pH.

    The problem is that aquarium water almost always has other sources of alkalinity and acidity other than carbonates and carbon dioxide, so the relationship isn't correct in most aquariums. That is why so many of us have "measured" our CO2 at 100+ ppm using that relationship, but the fish are not showing any effect. We do know that long before the CO2 concentration gets that high, all of the fish will die.

    The answer to this problem is a drop checker. See the relevant threads on this forum.
     
  3. Tom Barr

    Tom Barr Founder
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    At such low KH's and that generally most test kits suggest more rather than less, this water seems pretty pure.

    I do not think there is anything wrong here.
    Plant growth is good, focus more on the bubble rate generally and try and relate that to plant growth.

    Then also do the drop checker as a back up.

    also , make sure there is enough surface movement, do not try to stingy with that to conserve CO2, you can always add a bit more to make up for any loss, this will prevent fish gassing etc due to low O2.

    Folks often complain they cannot get enough CO2 with harming fish, but they'd also have the same gasping fish issue without CO2 if you do not circulate the water also:p

    Basically it adds more O2, good for fish and allows a lot more flexibility in adding CO2.

    Regards,
    Tom Barr
     
  4. herns

    herns Guru Class Expert

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    Newbie here...What is the problem of High KH?

    I ve been using a test kit that doesnt even show the starting color when I test my KH. Ive been dropping the solution one at a time by neither the starting color nor the end matches form the color. I live in Los Angeles area.

    thanks!
     
  5. VaughnH

    VaughnH Lifetime Charter Member
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    High KH is a problem for some plants, but not many. And, a few fish prefer lower KH. So, since low KH doesn't appear to cause anything bad to happen many of us prefer to use low KH.

    It sounds like your KH test kit is defective. My Aquarium Pharmaceuticals test kit gives a pretty easy to see color at both the starting color and the end color. My API GH kit, on the other hand, doesn't always work at all.
     
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