Ferplast CO2 test – inconsistent results

Discussion in 'Carbon Dioxide (CO2)' started by Amoeba, 25 Mar 2008.

  1. Amoeba

    Amoeba Member

    24 Mar 2008
    I used to measure PH and KH to estimate CO2 levels in my tank, however after some time noticed that the PH seems to be quite high regardless of fairly high BPS.
    To double check I have bought the Ferplast CO2 test.
    It turned out that the CO2 levels measured with the Ferplast test are twice as high as the ones calculated using PH and KH.

    I was not happy with such a huge difference and decided to give a drop checked a go (a glass one from ebay). Added around 4ml of 4KH solution (RO + baking soda) and 2 drops of Hagen LR PH test.

    Here is the problem. The CO2 levels calculated using the KH and PH of the water in my tank are consistent with the levels shown by the drop checked, but the Ferplast tests suggests the concentration of CO2 is twice as high.

    Does anybody have any experience with the Ferplast test?


    B.T.W. With the Ferplast test I use 20ml of tank water, 5 drops of solution1, and add drop by drop solution 2. The water turns pink after adding 14 drops, what according to the user’s manual equals 28ppm of CO2
  2. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    11 Jul 2007
    Chicago, USA
    Hi and welcome to the forum. It might be helpful to review this thread: viewtopic.php?f=36&t=467

    Using tank water to measure CO2 will always cause corrupted results. Drop checkers are slow to respond so the results may take hours. Measuring CO2 with the tools we have is difficult and inexact.


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