Tolerance of Nile tilapia juveniles to highly acidic rearing water

The present work aimed at determining the tolerance of Nile tilapia juveniles to highly acidic rearing waters and the effects of water acidity on the quality of tank effluents. The experimental design consisted of four treatments with different water pH values (4.12 ± 0.84; 5.13 ± 0.74; 6.14 ± 0.64 and 8.06 ± 0.48), with five replicates each. No exchange of water was performed throughout the study, only water replenishment to maintain the initial level. Variables of water quality, soil, growth performance, metabolism and effluents were monitored for eight weeks. Despite the lower total ammonia nitrogen (TAN) concentration in the pH 8 tanks, their levels of non-ionized ammonia (NH3) were the highest ones. At the end, the lowest body weight of fish was observed in the pH 8 tanks. There was a significant improvement in feed conversion ratio (FCR) and protein efficiency ratio (PER) due to to water acidification. There were reduced concentrations of NH3 in the acidified tanks' effluents. It was concluded that the gradual water acidification up to pH 4 can improve the Nile tilapia juveniles' growth performance.

本研究旨在探究尼罗罗非鱼（Nile tilapia）幼鱼对高酸性养殖水体的耐受能力，以及水体酸度对养殖池排放废水水质的影响。实验设置4组不同pH值的养殖水体处理组，各组pH分别为4.12±0.84、5.13±0.74、6.14±0.64及8.06±0.48，每组设置5个重复。实验全程未进行水体交换，仅通过补水维持初始水位。本研究周期为8周，期间监测了水质、底质、生长性能、代谢及排放废水相关指标。结果表明，尽管pH 8组养殖水体的总氨氮（total ammonia nitrogen, TAN）浓度较低，但其非离子氨（non-ionized ammonia, NH3）水平为所有组别最高；实验结束时，该组罗非鱼的体质量最低。水体酸化可显著改善饲料转化率（feed conversion ratio, FCR）与蛋白质效率比（protein efficiency ratio, PER），酸化处理组的养殖池排放废水中非离子氨浓度显著降低。综上，将养殖水体pH逐步酸化至4，可有效提升尼罗罗非鱼幼鱼的生长性能。