PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

A major protein source in Malaysia is Oreochromis niloticus, and its development is greatly influenced by the level of dissolved oxygen (DO). This research was done to determine the effects of DO on O. niloticus development, survival and feeding rate, as well as the potential of Egeria densa as a natural oxygenator in place of oxygen pumps. This study hypothesises that E. densa serves as a natural oxygenator, enhancing DO levels and promoting growth, survival, and feeding rate in O. niloticus. Three tanks with 50 O. niloticus each were assigned as Tank A (control), Tank B (E. densa), and Tank C (with an oxygen pump). The fish were fed bran twice daily, with feed amounts adjusted weekly based on mean body weight, over a 12-week experimental period. Survival rate (SR%), weight-gained (WG%), specific growth-rates (SGR%), feed conversion ratio (FCR%) and mortality-rate (MR%) were manually calculated, while the feed utilisation, growth performance, and water parameters were statistically analysed using Minitab 21 and Microsoft Excel. Overall, mean length and weight differed significantly (p<0.05) among tanks (p=0.000). In Tank C, length differed significantly between fish with and without oxygen (p=0.006), whereas weight did not (p=0.442; p>0.05). The length-weight regression analysis (LWRs) showed DO has a significant impact on O. niloticus' growth rate with negative allometric (Tank A, b=2.6828; Tank B, b=2.5248), and isometric (Tank C, b=3.0084). The highest SR% with the lowest MR% and FCR% was shown in Tank C. E. densa respiration competes for DO, making it unsuitable to replace air pumps in aquaculture systems.