The utilization of algae in aquaculture is environmentally friendly, safe, and cost-effective and can effectively substitute for fish meal and fish oil in aquatic feeds. Incorporating algae as dietary supplements leads to significant enhancements in aquatic animals’ health and also improves the aquatic ecosystem. Algae are rich sources of nutrients and serve as the foundational food source in the aquatic food chain. Currently, 40 different algae species are employed in aquaculture. Furthermore, algae contributes to elevating the overall quality of aquatic feed products. Aquaculture stands as the most vital food production sector globally; however, challenges such as infection outbreaks and aquatic environmental pollution pose significant threats to the sustainable growth of this industry. An alternative strategy for mitigating environmental issues and improving aquatic production involves the utilization of algae. The novelty in the applications of algae in aquaculture stems from their multifaceted roles and benefits, such as their capacity to improve water quality, serve as nutrient-rich feed supplements, and enhance the overall health and productivity of aquatic species. These versatile applications of algae represent a fresh and innovative approach to sustainable aquaculture practices. This review furnishes insights into the use of algae, algae extracts, or components derived from algae to enhance water quality. Additionally, it covers the utilization of algae-based feed supplements, boosting of the immune system, enhanced growth performance, and disease resistance in aquatic animals.

Nile tilapia, Oreochromis niloticus, (2.00 ± 0.02 g) were reared in 16 70‐L tanks (40 individual/tank) and fed diets (approx. 345 g/kg protein, approx. 87 g/kg crude fat) containing 0 (CTL), 75 (PH‐75), 150 (PH‐150), and 300 (PH‐300) mg/kg phytol (n = 4). After 60 days of feeding (4% daily), growth performance, humoral immune parameters, and gut bacteria were analyzed. Also, hepatic antioxidant parameters were determined before and after the fish were transported in plastic bags for 6 hr. The results showed that PH‐75 exhibited the highest final weight (P < 0.001), weight gain (P < 0.001), feed intake (P < 0.001), feed efficiency (P = 0.015), plasma lysozyme activity (P = 0.004), and intestinal Lactobacillus sp. population (P = 0.017), among the treatments. The highest plasma alternative complement activity (P = 0.006) and the lowest intestinal total viable bacteria (P = 0.027) were observed in PH‐75 and PH‐150. The highest plasma alkaline phosphatase activities were observed in PH‐75 and PH‐300 (P = 0.014). The highest blood leukocyte (P = 0.008), monocyte (P = 0.010), and eosinophil (P < 0.001) were observed in PH‐300, while the highest blood neutrophil was observed in all phytol treatments (P < 0.001). The highest hepatic lipid peroxidation was observed in PH‐300, whereas PH‐75 and PH‐150 showed the lowest values (P < 0.001). The highest hepatic reduced glutathione was observed in PH‐75, also PH‐150 exhibited significant elevation in this parameter, compared to CTL (P < 0.001). Transportation led to significant elevations in the hepatic antioxidant enzymes’ activities in CTL, PH‐75, and PH‐150; the highest activities were related to PH‐75 and PH‐150 treatments, which had also the highest post‐transportation survivals (P < 0.001). In conclusion, phytol is a suitable feed supplement for Nile tilapia, improving growth performance and welfare, particularly at 75 mg/kg.