水质调节被广泛认为是水产养殖领域中一种高效的疾病预防策略，并具有可持续水产养殖发展的显著潜力。本研究将四种水质调节剂——过硫酸单壳素钾（KMPS）、磷酸羟甲基膦（THPS）、枯草芽孢杆菌（BS）和壳聚糖（CS）定期添加至尼罗罗非鱼（GIFT罗非鱼）的养殖水中。随后，通过测量GIFT罗非鱼的水质指数、日增长相关性能和免疫指标，全面评估了这四种水质调节剂对GIFT罗非鱼的影响。研究结果表明，采用这四种水质调节剂可使水中氨氮、活性磷酸盐、亚硝酸盐、总有机碳（TOC）和化学需氧量（COD）的含量降低。此外，这些调节剂能有效维持水中的溶解氧（DO）水平和pH值。此外，使用这些调节剂对GIFT罗非鱼的各种生理参数均有积极影响，包括最终体重、体重增长率（WGR）、特定生长率（SGR）、体况因子（CF）、饲料转化率（FCR）、脾脏指数（SI）、肝脏指数（HSI）、免疫细胞计数、抗氧化相关酶（一氧化氮，NO和超氧化物歧化酶，SOD）的活性以及肝脏和脾脏免疫相关因子（肿瘤坏死因子-α，TNF-α和白细胞介素-1β，IL-1β）的mRNA表达水平。值得注意的是，BS和CS水质调节剂处理组的改善效果最显著。此外，与对照组相比，BS和CS组的血清白蛋白（ALB）和总蛋白（TP）水平显著升高（P <0.05），而其他指标差异不显著（P >0.05）。然而，KMPS和THPS组的GIFT罗非鱼血清门冬氨酸氨基转移酶（AST）、丙氨酸转氨酶（ALT）、肌酐（CRE）和血尿素氮（BUN）水平显著升高（P <0.05），同时显著降低肝脏指数（P <0.05）。此外，局部病理观察发现肝脏细胞内有空泡、核萎缩和嗜酸性小体。综上所述，这四种水质调节剂，主要是BS和CS，可以通过调节水质进而增加GIFT罗非鱼免疫相关因子的表达水平或抗氧化相关酶的活性，从而以不同程度改善GIFT罗非鱼的生长性能和免疫能力。相反，持续使用KMPS和THPS可能会逐渐减弱它们促进生长的特性，并可能阻碍GIFT罗非鱼的生长。版权：©2023年Wang等人。本文为开放获取文章，根据创作共用许可证分发，允许在任何媒体中进行无限制的使用、发布和复制，前提是原始作者和来源被归属。

Water quality regulation is widely recognized as a highly effective strategy for disease prevention in the field of aquaculture, and it holds significant potential for the development of sustainable aquaculture. Herein, four water quality regulators, including potassium monopersulfate (KMPS), tetrakis hydroxymethyl phosphonium sulfate (THPS), bacillus subtilis (BS), and chitosan (CS), were added to the culture water of Oreochromis niloticus (GIFT tilapia) every seven days. Subsequently, the effects of these four water quality regulators on GIFT tilapia were comprehensively evaluated by measuring the water quality index of daily growth-related performance and immune indexes of GIFT tilapia. The findings indicated that implementing the four water quality regulators resulted in a decrease in the content of ammonia nitrogen, active phosphate, nitrite, total organic carbon (TOC), and chemical oxygen demand (COD) in the water. Additionally, these regulators were found to maintain dissolved oxygen (DO) levels and pH of the water effectively. Furthermore, using these regulators demonstrated positive effects on various physiological parameters of GIFT tilapia, including improvements in final body weight, weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), feed conversion ratio (FCR), spleen index (SI), hepato-somatic index (HSI), immune cell count, the activity of antioxidant-related enzymes (Nitric oxide, NO and Superoxide dismutase, SOD), and mRNA expression levels of immunity-related factors (Tumor Necrosis Factor-alpha, TNF-α and Interleukin-1 beta, IL-1β) in the liver and spleen. Notably, the most significant improvements were observed in the groups treated with the BS and CS water quality regulators. Moreover, BS and CS groups exhibited significantly higher serum levels of albumin (ALB) and total protein (TP) (P < 0.05), whereas the other indicators showed no significant difference (P > 0.05) compared to the control group. However, the KMPS and THPS groups of GIFT tilapia exhibited significantly higher serum levels of aspartate aminotransferase (AST), alanine transaminase (ALT), creatinine (CRE) and blood urea nitrogen (BUN) (P < 0.05), whereas they exhibited significantly decreased HSI (P < 0.05). In addition, the partially pathological observations revealed the presence of cell vacuolation, nuclear shrinkage, and pyknosis within the liver. In conclusion, these four water quality regulators, mainly BS and CS, could improve the growth performance and immunity of GIFT tilapia to varying degrees by regulating the water quality and then further increasing the expression levels of immune-related factors or the activity of antioxidant-related enzymes of GIFT tilapia. On the contrary, the prolonged use of KMPS and THPS may gradually diminish their growth-enhancing properties and potentially hinder the growth of GIFT tilapia.Copyright: © 2023 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.