The post-hoc analysis (Tukey B) framed the mean values of DO corresponding to the four rearing units in two distinctive subsets of values; mean DO values registered for B1 and B2 tanks were significant different comparing with B3 and B4 tanks. Concerning the dynamics of the metabolism and nitrification products, they maintained within the optimal range, the average values of nitrate, nitrite, ammonia and phosphates being centralized in figure 2.