Farmed catfish (Clarias gariepinus and Pangasius hypophthalmus) represent a cornerstone of global aquaculture, yet disease outbreaks pose significant threats to production. Algal-based feed additives, derived from microalgae like Spirulina platensis and macroalgae such as Chaetomorpha aerea, offer a sustainable solution by enhancing innate immunity, antioxidant capacity, and disease resistance. Rich in polysaccharides, carotenoids, and polyunsaturated fatty acids (PUFAs), these additives modulate immune responses without antibiotic residues. This article reviews the mechanisms of algal supplementation in catfish, including improved lysozyme activity, phagocytic indices, and gut microbiota modulation. Drawing from recent studies, we discuss formulation strategies, dosage optimization, and economic viability. Challenges like algal biomass scalability and variability in bioactive compounds are addressed, alongside future prospects for integrated aquaculture. By promoting eco-friendly immunity boosters, algal additives can reduce mortality rates by up to 30% and support sustainable catfish farming.