API AMMONIA TEST KIT
If you keep fish, your water has ammonia. Fish release ammonia from their gills. It is a waste product of their metabolic processes. In properly cycled tanks, the bacteria in your tanks consumes the ammonia and produces Nitrite. Therefore in a healthy tank, the concentration of ammonia in your water should always be low enough to be undetectable by a test kit. However, if you are just starting a tank, or if you dosed your tank with antibiotics that eliminated your biological filtration, your tank WILL have an ammonia spike.
Ammonia is lethal to fish even in small concentrations.
The best way to monitor your tanks progress while it cycles is with a dedicated Ammonia test kit. API's Ammonia test kit is what we use whenever we set up new tanks or environments. It is free of toxic metals, and will function properly in both fresh and saltwater.
This test kit will measure from 0ppm to 8ppm of ammonia.