Coastal Aquaculture and Mariculture (2+1)

Unit 4 - Water and soil quality management

4.1.2.e. Ammonia

• Ammonia exists in water in two states, ionized ammonia, also called the ammonium ion (NH4+) and un-ionized ammonia (NH3). The sum of two is called total ammonia or simply ammonia.
• The toxicity of total ammonia depends on what fraction of the total is in the un-ionized form, since this form is by far the more toxic of the two.
• Which fraction dominates depends on the pH, temperature and salinity of water; out of this water pH has the strongest influence.
• At higher pH un-ionized ammonia dominates and hence more toxic. A maximum concentration of 0.01mg/L is recommended for marine fish.