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30 July 2020

In water quality analysis, it is industry standard to report nitrogen compounds in terms of nitrogen content (e.g. NH₃-N, NO₂-N, NO₃-N etc) rather than the concentration of the ion/compound (NH₄⁺/NH₃, NO₂^-, NO₃^-).  Consequently, our Ammonia, Nitrite and Nitrate test kits follow this industry standard.  While calculations can be performed to convert the reported value to the concentration of the ion, there are some very good reasons why this should be avoided. 

To clarify the distinction between these two methods of reporting, it’s a bit like attempting to count vehicles on a road by counting the number of wheels.  The problem is that, motorbikes will have two wheels, some cars might only have three, whilst lorries may have more than four.  From this example, the number of wheels is largely irrelevant and really we should just count the vehicles instead.  The same is true for the nitrogen compounds – we don’t necessarily need to report the number of other atoms attached to the nitrogen. 

Looking at some of the pioneering and well-respected documentation that discusses the toxicity of nitrogen compounds as they relate to fish health, values for ammonia and nitrite are reported in terms of nitrogen.  As such, the results from our tests are directly comparable with those of toxicity data.  Looking through various websites and contemporary books that also suggest toxicity data,  the numerical values are the same, but there are multiple instances where the units of measurement are not reported.  It should be made clear that these toxicity values we use to ensure our fish are living in a safe environment is actually in terms of nitrogen.  An incorrect assumption that these toxicity values are in terms of the ion concentration combined with the use of a kit that reports in the same fashion will therefore lead one to believing that the concentration of a compound is much higher than it should be.  The consequence? Unnecessary water changes, wasted products in attempting to resolve a problem that doesn’t exist, not to mention the distress caused to the fish keeper!

Of course, if you prefer to work in terms of concentration of ion, you can multiply the results generated by our kits by 1.12 for ammonia, 3.29 for nitrite and 4.43 for nitrate, but be aware of what that result means and how it relates to the target you’re trying to achieve.  It’s very likely that modern literature quotes values without presenting the units properly.  Equally, if using kits where concentration of ion is reported, you should divide the result by one of the figures above for a correct comparison to toxicity data from published sources and our kits.

Tagged in: Indoor, Outdoor