In an intensive land based fish farming system, the toxicity
of excreted nitrogenous compounds is often a limiting factor
(Bradfield, 1985). The toxicity of TAN(the totalNH3–NandNH4
+–N)
increases with the pH of the water because TAN enters the organism
as NH3 and the proportion of NH3 increases with higher pH
(Randall and Tsui, 2002).