Macherey-Nagel test strips for ammonia, in one presentation.
90714
A semi-quantitative test strip for ammonia, the free form that is toxic to fish. Dip it, wait the stated time, and compare the pad against the colour scale on the tube.
Ammonia is the fraction of the ammonium total that actually does the damage, and how much of it exists depends on temperature and pH. Measuring it directly answers the question a total-ammonium figure only implies.
A strip gives a range, not a figure. That is enough for the great majority of decisions — dose or do not dose, discharge or hold, keep running or stop — and it gives the answer where the sample is, in about a minute, with no instrument to calibrate and nothing to carry back to a laboratory.
When a number has to be defensible — a regulatory report, a dispute, a limit you are close to — a photometer or a laboratory method is the right tool. The strip's job is to tell you whether you need one.
Warm water and high pH both push the balance toward free ammonia; the same total is far more dangerous in an afternoon pond than a morning one.
Supplied in one presentation.