Macherey-Nagel test strips for ammonium, in one presentation.
91315
A semi-quantitative test strip for ammonium, the first nitrogen compound to appear when organic matter breaks down. Dip it, wait the stated time, and compare the pad against the colour scale on the tube.
It is the earliest warning of a failing filter, a dead fish nobody found, or organic contamination reaching a well. It is also directly toxic to fish, more so as the water warms and the pH rises.
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.
The same total reading is far more dangerous at pH 8.5 than at pH 7, because more of it exists as free ammonia.
Supplied in one presentation.