Water quality management in shrimp ponds cannot be separated from the control of nitrogen compounds. These compounds play an essential role in the pond ecosystem, however poor management can degrade water quality and directly impact shrimp health and growth.
Read this article to understand the role of nitrogen and how to control it in shrimp ponds effectively!
Types of Nitrogen Compounds in Shrimp Ponds
Nitrogen compounds commonly found in shrimp ponds include ammonia, nitrite, and nitrate. Ammonia exists in water in two forms: unionized ammonia (NH₃) and ionized ammonia, also known as ammonium (NH₄⁺). In pond monitoring, ammonia is typically measured as Total Ammonia Nitrogen (TAN), which represents the combined concentration of both forms.
The proportion of unionized and ionized ammonia is strongly influenced by water pH and temperature. Under high pH and temperature conditions, the proportion of unionized ammonia increases. This form is the most toxic to aquatic organisms. In general, the safe TAN level in shrimp ponds is 0.1 ppm, while unionized ammonia concentrations above 0.6 ppm can be lethal. Interestingly, higher CO₂ concentrations can reduce ammonia toxicity by lowering water pH, thereby limiting the formation of unionized ammonia.
Factors Affecting Ammonia Toxicity
Ammonia toxicity is not determined solely by its concentration but is also influenced by several environmental and biological factors. pH is a key factor; an increase in pH to around 9 can significantly increase ammonia toxicity and pose a serious risk of shrimp mortality.
Salinity also plays an important role. At high salinity levels (up to 40 ppt), ammonia tends to be less toxic. In contrast, at lower salinity levels (around 15 ppt), ammonia toxicity can increase. Dissolved oxygen (DO) is critical for the conversion of ammonia into nitrite and nitrate. The oxidation of nitrite into nitrate requires more oxygen than the conversion of ammonia into nitrite.
Water temperature affects the balance between ammonia forms. Higher temperatures increase the proportion of unionized ammonia, thereby increasing its toxicity. In addition to environmental factors, shrimp age also influences tolerance levels. Older shrimp tend to be more tolerant of ammonia, while younger shrimp are much more susceptible. Ammonia accumulation can reduce water quality, increase oxygen demand, and ultimately slow shrimp growth.
