Locally available feedstuffs, such as grain seed cakes, oilseeds, and vegetable waste, hold immense potential as alternative feed sources in fish farming. However, these plant-based ingredients have low crude protein content and lack essential fatty acids, which lowers palatability and feed conversion efficiencies, leading to suboptimal fish growth. Traditional feedstuffs like fishmeal and soybean meal face sustainability challenges such as local unavailability, the presence of anti-nutritional factors, and energy-intensive processing. The rising costs of commercial aqua-feeds and feed scarcity necessitate exploring alternative fish feed options. Aquatic plants like Ipomoea aquatica, Lemna minor, and Azolla pinnata, along with green and blue-green microalgae such as Chlorella spp. and Arthrospira spp. (Spirulina), are promising alternatives due to their high protein content, availability of essential omega-3 fatty acids such as EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid), and beneficial bioactive compounds. These plants and microalgae, with crude protein content ranging from 25% to 65%, can significantly enhance fish growth, health, and product quality by partially or entirely replacing fishmeal. Their nitrogen-fixing abilities contribute to their high protein levels. Additionally, these organisms have various biotechnological applications, including phytoremediation, Integrated Multi-trophic Aquaculture (IMTA), aquaponics, biofloc technology, and constructed wetlands. Despite their potential, challenges in scaling up and integrating these alternatives into existing systems remain. Collaborative efforts and advocacy among farmer groups are crucial for knowledge sharing and fostering sustainable biotechnological solutions. Long-term strategies should focus on upscaling local feed production and research and development to achieve self-sufficiency and cost-effective natural feed production systems in fish farming.
