What is the difference between test kit readings of ammonia ion and ammonia/nitrogen?
Many aquarists and pond keepers are perplexed by the use of the terms ammonia ion and ammonia/nitrogen (or ammonia as nitrogen), and do not know what the difference is between the two. The differences between the two terms are in how the chemical composition of the same ammonia molecules are being measured, which can be in two different ways, giving two different readings, each of which is correct. If you have a reading specified as ammonia/nitrogen it can be converted to ammonia ion by multiplying the reading by 1.3. If the reading is expressed as ammonia ion, it can be converted to ammonia/nitrogen by dividing by 1.3. For example, if the ammonia ion reading is 2.6 ppm, you can divide by 1.3 and you will get an ammonia/nitrogen reading of 2.0 ppm (2.6 ÷ 1.3 = 2.0). The conversion factor of 1.3 is based on the atomic weight proportions of nitrogen and hydrogen in ammonia (1.3 weight units of ammonia contain 1.0 weight units of nitrogen). If the ammonia is measured as the total molecula
