At any given pH, more toxic ammonia is present in warmer water than in cooler water ( Fig 1). The equilibrium between NH 3 and NH 4 + is also affected by temperature. Therefore, the toxic form of ammonia predominates during the late afternoon and early evening ( Fig 2) and ammonium predominates from before sunrise through early morning. In ponds, pH fluctuates with the photosynthesis (which increases pH) and respiration (which reduces pH) of pond organisms. Now, simply multiply that number (divided by 100) by the total ammonia concentration to estimate the un-ionised ammonia concentration. That point is an estimate of the percentage of un-ionised ammonia in the water sample. From that point, draw a line to the right until it intersects the graphвЂ™s vertical axis. To determine the proportion of un-ionised ammonia in a water sample, draw a line from the pH of the water straight up to the line that is closest to the water temperature. However, this proportion increases dramatically as pH increases ( Fig 1). In general, less than 10 percent of ammonia is in the toxic form when pH is less than 8.0. Ammonium ion is relatively nontoxic and predominates when pH is low. Un-ionised ammonia is the toxic form and predominates when pH is high. The value is reported as вЂњtotal ammoniaвЂќ or simply вЂњammonia.вЂќ (In this publication, вЂњammoniaвЂќ refers to the sum of both forms the specific forms will be referred to as appropriate.) The relative proportion of the two forms present in water is mainly affected by pH. The techniques used to measure ammonia provide a value that is the sum of both forms.

Effects of pH and temperature on ammonia toxicityДЄmmonia in water is either un-ionised ammonia (NH 3) or the ammonium ion (NH 4 +). However, ammonia can have so-called вЂњsublethalвЂќ effects-such as reduced growth, poor feed conversion, and reduced disease resistance-at concentrations that are lower than lethal concentrations. In properly managed fish ponds, ammonia seldom accumulates to lethal concentrations. If the ammonia concentration gets high enough, the fish will become lethargic and eventually fall into a coma and die. When ammonia accumulates to toxic levels, fish can not extract energy from feed efficiently. Ammonia is toxic to fish if allowed to accumulate in fish production systems.

Ph of dilute ammonia solution