Immobilized microalgae are a promising approach to incorporate microalgae in recirculating aquaculture system (RAS) for water purification. In the present study, two types of biosorbents including sodium alginate–immobilized Scenedesmus spp. and Chlorella spp. beads (algal beads) and sodium alginate beads without microalgae (alginate beads) were prepared. In the first experiment (static test), the potential of two biosorbents to remove different concentrations of total ammonia nitrogen (TAN) and total phosphorus (TP) from water was investigated. In the second experiment, two prepared biosorbents were used as biofilter in a RAS for rearing African cichlid (Labidochromis lividus) for 30 days. The survival rate and growth indices of fingerling fish and removal efficiency of two biosorbents for TAN, NO₃^—N, and TP were determined. The results of static test showed that the removal efficiency and uptake capacity of the two biosorbents for TAN and TP increased during 30 days of the experiment, and these values for the algal beads were higher than the alginate beads. The TAN removal efficiency of the two biosorbents increased with increasing TAN concentration from 0.5 to 5 mg L⁻¹. The application of algal beads in the RAS improved the survival rate, final weight, final length, weight gain, and daily growth index (DGI%) indices of fish compared to those cultured in the RAS containing the alginate beads and the control (P<0.05). The algal and alginate beads decreased the TAN concentration by 42.85% and 28.57% compared to the control after 30 days of cultivation period, respectively. The uptake of nitrate was not observed by the two biosorbents during cultivation period. The TP removal efficiency of algal beads reached 44.90% after 30 days. The findings of this study indicated that the sodium alginate–immobilized microalgae could be considered as a suitable biofilter to be incorporated into a RAS to improve water quality and consequently enhance the growth and health of fish.

固定化微藻是一种很有前途的方法，可以将微藻纳入循环水产养殖系统 (RAS) 以净化水质。在本研究中，两种类型的生物吸附剂，包括海藻酸钠固定化栅藻属。和小球藻属。制备了不含微藻的珠（藻珠）和藻酸钠珠（藻酸盐珠）。在第一个实验（静态测试）中，研究了两种生物吸附剂从水中去除不同浓度的总氨氮 (TAN) 和总磷 (TP) 的潜力。在第二个实验中，两种制备的生物吸附剂被用作 RAS 中的生物过滤器，用于饲养非洲慈鲷 ( Labidochromis lividus)) 30 天。测定了鱼种的存活率和生长指数以及两种生物吸附剂对TAN、NO ₃ ^{- N和TP的去除效率。}静态测试结果表明，在 30 天的实验期间，两种生物吸附剂对 TAN 和 TP 的去除效率和吸收能力均有所增加，并且藻珠的这些值高于藻酸盐珠。两种生物吸附剂的 TAN 去除效率随着 TAN 浓度从 0.5 增加到 5 mg L ^-1而增加。与在含有藻酸盐珠的 RAS 和对照中培养的那些相比，在 RAS 中应用藻珠提高了鱼的存活率、最终重量、最终长度、增重和日生长指数 (DGI%) 指标（P<0.05)。在培养 30 天后，与对照相比，藻类和藻酸盐珠的 TAN 浓度分别降低了 42.85% 和 28.57%。在培养期间，两种生物吸附剂未观察到硝酸盐的吸收。30天后藻珠的TP去除效率达到44.90%。这项研究的结果表明，海藻酸钠固定化微藻可被视为一种合适的生物过滤器，可纳入 RAS 以改善水质，从而促进鱼类的生长和健康。