Aquaculture is one of the most dynamic branches of food production for human consumption. Global aquaculture increasingly relies on diverse culture systems, principally pond-based, biofloc technology systems (BFT) and recirculating aquaculture systems (RAS). These systems expose fish to distinct environmental and management stressors that can cause oxidative stress (OS), as a central physiological response of fish exposed to suboptimal environmental and husbandry conditions, with direct effects on digestive physiology, nutrient assimilation and growth. The gastrointestinal tract is both a target and a mediator of OS, integrating signals that influence digestion, nutrient absorption, and microbial homeostasis. This review synthesizes current knowledge on generation mechanisms of OS in fish, the resulting biochemical and histological alterations in digestive function, and practical strategies to mitigate these effects in different aquaculture systems. Highlighting system-specific stressors and adaptive responses, particular attention is given to antioxidant enzymes, digestive enzyme activity, intestinal morphology, and gut microbiota shifts under oxidative challenges. Key findings are: (1) elevated stocking density, poor water quality, hypoxia, and accumulation of metabolic wastes are consistent OS drivers across systems but are often more acute in RAS if poorly managed and in crowded ponds; (2) OS frequently correlates with reduced activities of digestive enzymes, altered gut histomorphology and dysbiosis of gut microbiota, impairing feed conversion and growth; (3) antioxidant supplementation, probiotics/prebiotics and optimized husbandry reduce OS markers and partially restore digestive function. The review concludes with research gaps and management recommendations for maintaining redox balance and digestive efficiency in cultured fish species to support resilient aquaculture.