Effect of Water De-stratification on Dissolved Oxygen and Ammonia in Tilapia Ponds in Northern Thailand

For Nile tilapia cultured in earthen ponds in Thailand, mortality from disease outbreak frequently occurs when dissolved oxygen (DO) levels are low and ammonia concentrations are high. Repeated analysis of variance (ANOVA) showed that water depth and fish culture systems have significant effects on total ammonia nitrogen (TAN). TAN concentrations near the surface were lower than at the bottom, and increased after water de-stratification. TAN in the integrated culture system was significantly higher than in commercial and subsistence systems. Effects of de-stratification on pond water quality provided by this study are useful towards improved pond management practices and monitoring DO thresholds