Ammonia Test Kit Guide
Why ammonia is the most toxic nitrogen compound in an aquarium, how reagent test kits detect it, and why the target reading is always zero.
What it measures
An ammonia test kit measures the concentration of ammonia, written as NH3 and NH4+, in aquarium water. Ammonia is the most toxic nitrogen compound in an aquarium and is produced whenever fish produce waste. The kit reports the result in parts per million (ppm).
Why ammonia is dangerous
Ammonia is highly toxic to fish; it can burn fish gills and skin and is harmful even at low concentrations. Because it builds up rapidly, any detectable ammonia reading in a stocked tank is an emergency that calls for an immediate water change and investigation of the cause.
Where ammonia comes from
Whenever fish produce waste, some ammonia enters the water. Uneaten food and decaying matter add to it. In a mature, biologically filtered tank, beneficial bacteria consume this ammonia and convert it to nitrite as part of the nitrogen cycle, so a healthy tank reads zero.
Target reading
The goal is to measure 0 ppm ammonia in tank water at all times. A non-zero result means the biological filter cannot process the current waste load, which can happen in a new tank, after adding many fish at once, or if the filter has been disrupted.
How reagent kits work
Liquid reagent test kits add chemical reagents to a measured tube of tank water; the sample changes colour according to the ammonia concentration, and the colour is matched against a printed chart. Test strips work similarly with a colour pad but are generally read more coarsely. Either way, the result is a colour-to-number comparison.
When to test
- Daily during the cycling of a new tank, then less often as the cycle matures.
- After adding new fish or increasing the stocking level.
- Whenever fish show signs of distress or after a filter problem.
- As part of routine checks every one to four weeks in an established tank.
Using the kit
- Fill the test tube to the marked line with tank water.
- Add the reagent drops exactly as the instructions specify and cap and shake if required.
- Wait the stated development time before reading the colour.
- Compare against the chart in consistent, neutral lighting and rinse the tube afterwards.