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    Version as of 20:32, 18 May 2021

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    The first step is to understand the difference between ammonium NH4 and free ammonia NH3.
    There is a lot of confusion about NH4 and NH3 so let us and try and explain.

    NH3 (ammonia) is a gas and sometimes called free ammonia it is the toxic part of total ammonia nitrogen (TAN) which is NH3 + NH4.  It is very difficult to work out how much harmful NH3 is present by measuring NH4 and PH and then using a look up table. Most test kits measure NH4 even if they are marked as an NH3/NH4 test kit, this is done by changing the pH of the water sample; you may have noticed how ammonia test kits normally have a small bottle marked harmfull corrosive.

    Seneye only measures toxic free ammonia, NH3 and in very low levels.

    NH3 is reported in the unit of ppm but this is interchangble with mg/L as it is a gas disolved in water.


    Ammonia toxicity changes for different organisms but one thing is constant and that the desired level is as close to zero as is possible. Marine organisms and fish tend to be more sensitive and where as fish that have evolved to live in ponds or puddles such as carp or paridise fish tend to be less so.


    As a rule of thumb and if measured directly we use the following chart.

    NH3 level  PPM PPM
    safe 0.000 0.020
    alert 0.020 0.050
    alarm 0.050 0.200
    toxic 0.200 0.500
    deadly 0.500+  




    If your ammonia is very high you may find it useful to learn how to control ammonia.

    Why does my free ammonia NH3 go up when I do water changes?

    Can my seneye be used for cycling my aquarium?