Fig. 1

Total ammonia nitrogen (TAN), unionized ammonia (NH3) and nitrite (NO2) concentrations in culture water tanks of Chelon ramada fed a basal diet containing varying levels of rosemary oil and/or Zymogen Forte during a 75-day rearing trial using brackish groundwater. (T1) = fish fed BD without RO or ZF (control); (T2) = fish fed the BD containing 0.5 g of RO kg− 1; (T3) = fish fed BD containing 0.5 g of RO and 1 g of ZF kg− 1; (T4) = fish fed BD containing 1.0 g of RO kg− 1; and (T5) = fish fed BD containing 1 g of RO and 1 g of ZF kg− 1. Abbreviations: BD = basal diet; RO = rosemary oil; ZF = Zymogen Forte