Red Seaweeds in Aquaculture: Impacts on growth, immunity, antioxidant status, gene expression, and gut health

Abstract Red seaweeds ( Rhodophyta ) and their polysaccharides represent promising, sustainable solutions for boosting aquaculture productivity. Rich in bioactive compounds such as carrageenan, agar, and sulfated galactans, these seaweeds have demonstrated the ability to improve growth, health, and disease resistance in various aquaculture species. This review examines the applications, benefits, and limitations of red seaweeds in aquaculture, with particular attention to their roles as feed binders, partial fishmeal replacements, feed supplements, and immunostimulants. Species such as Gracilaria , Kappaphycus , and Porphyra have been shown to enhance immune responses, promote gut health, and mitigate nutrient pollution in aquaculture systems. Despite these advantages, challenges remain, including high cultivation costs, variability in bioactivity, and supply chain constraints. This review highlights the growing potential of red seaweeds for sustainable aquaculture while identifying research needs related to dosage optimization, delivery strategies, and elucidating the molecular mechanisms of their effects. Supplementation with red seaweeds aligns with the United Nations’ Sustainable Development Goals, offering an eco-friendly alternative to antibiotics with the potential to yield both environmental and economic benefits in aquaculture.