Ammonia and ammonium are substances which should be converted rapidly into nitrite followed by nitrate and nitrogen gas. If this does not happen then the aquarium is not fully cycled or biological processes are not proceeding as they should.
The Salifert Ammonia test is very straightforward and measures the sum of toxic ammonia and ammonium in just a few minutes.
The kit can perform approx. 50 measurements and can detect 0.5 ppm of total ammonia easily.