Advances in Aquaculture Aeration Technologies: Comparative Review of Surface, Mixed-Layer, and Hypolimnetic Oxygenation Systems

Aquaculture is essential for global food production; however, ensuring optimal water quality and maintaining adequate dissolved oxygen levels poses a significant challenge. Oxygen depletion may occur not only at the surface but also in deeper stratified layers, particularly within the hypolimnion, where limited mixing can lead to persistent anoxia and associated ecological stress. This review provides a comprehensive, structured assessment of aeration technologies used in aquaculture, encompassing conventional surface aerators, mixed-layer enhancement systems, and dedicated hypolimnetic oxygenation systems. The surface aerators, including paddlewheel, spiral, and pump-sprayer systems, are examined with respect to hydrodynamic mixing mechanisms, oxygen transfer efficiency, and suitability for shallow and high-density culture systems. Their operational limitations in stratified water bodies are critically discussed. The review then evaluates advanced oxygenation approaches designed for deeper or stratified environments, including hypolimnetic oxygenation systems, venturi-based injectors, and microbubble generation technologies. Emphasis is placed on governing mass transfer mechanisms, gas transfer coefficients, bubble dynamics, energy efficiency, destratification effects, and environmental impacts. By comparatively analyzing design parameters, operational performance, scalability, and application constraints across small-scale and commercial aquaculture systems, this review provides a unified engineering perspective on aeration strategies. The synthesis clarifies the functional distinctions between surface-driven aeration and depth-targeted oxygenation technologies, providing guidance for selecting systems based on water-body morphology, stratification regime, and production objectives.