Aquaculture being one of the fastest growing food production sectors still possesses a significant challenge for maintaining optimal dissolved oxygen (DO) levels in farmed ponds particularly in intensive culture systems. Many times, the oxygen demand of the cultured organisms is not met by the natural aeration processes. Hence, the artificial aeration comes into play to support health, growth and productivity of the cultured organisms. Aeration methods like stepped cascades, perforated trays and shower systems have been studied for their ability to improve oxygen transfer by increasing air and water interaction. Cascade aerators are noted for their simplicity and low cost, making them ideal for small-scale farmers, however shower aeration systems show better performance than cascade aerators due to geometric optimization of designs. This review primarily discusses about the importance of cascade aerators and vertical aeration systems used in aquaculture practices highlighting the principle, design, efficiency and their further improvements suiting to the aquaculture practices. Though having a brief progress in research, there are still lack of understanding about the design performance, cost-effectiveness and practical feasibility of these systems under different pond aquaculture conditions. Comparative analysis of reported Standard Aeration Efficiency (SAE) (≈1.2-4.98 kg O₂/kWh) and Standard Oxygen Transfer Rate (SOTR) values among different cascade aerators, alongside case studies from wastewater and aquaculture applications, is used to identify factors governing aeration efficiency, scale limitations and field-level constraints. Building on these insights, the study discusses the development and pond-scale testing of AICRP on PEASEM, centre at ICAR-CIFA vertical aeration prototypes: cascade aerators and shower-based towers, that achieved 33-40% increase in pond DO and demonstrated their suitability for aerating 0.12 ha ponds with relatively low capital cost. The review contributes an integrated conceptual framework for next-generation vertical aeration towers that combine cascade and shower principles, enable continuous water recirculation and can be coupled with solar power and sensor-based automation to minimize energy use while maintaining optimal DO. By explicitly addressing the challenges of energy efficiency, design optimization, scalability and real-pond validation, this work outlines a pathway for replacing or complementing conventional mechanical aeration with cost-effective, environmentally sustainable gravity-driven systems in intensive aquaculture.

Aerator efficiency, Cascade aerator, Dissolved oxygen, Pond aeration, Shower aeration system, Vertical aeration towers

Aquaculture is emerging as one of the fastest growing sectors of the global fisheries. Recent advancements in aeration technology have significantly boosted the efficiency of the fish farming practices. Aeration through natural diffusion of oxygen into the water bodies particularly in the intensive aquaculture systems is insufficient to maintain optimal dissolved oxygen (DO) levels for the culture organisms. Following these conditions artificial aeration methods based on the utilization of external devices and processes to enhance water oxygenation resulting in optimal DO concentrations maintained in the system have been studied by various researchers (Kumar et al., 2013; Roy et al., 2017; Ochoa et al., 2022).

Dissolved oxygen (DO) is a critical factor of the aquacultural practices as it influences the health and survival of aquatic organisms. In freshwater aquaculture practices, insufficient DO levels become a major constraint on the aquatic organisms particularly in intensive aquaculture systems. At depleted DO levels in the system reduced fish growth and lesser production rates affects the overall sustainability and yield from culture operations (Sultana et al., 2017; Xiao et al., 2020; Yadav et al., 2021). Oxygen is a fundamental element required for the survival and physiological health of aerobic life forms. Within aquatic ecosystems, it serves as a vital component for respiration, however, its availability is often limited due to its low solubility in water. The concentration of oxygen in these environments is determined by several interacting variables, including atmospheric diffusion, fluctuations in water temperature and the oxygen released by aquatic vegetation during photosynthesis. These factors collectively determine the dissolved oxygen concentration available for the aquatic organisms (fish) for utilization (Burke et al., 2022). The DO levels needed to be checked and maintained as reduced levels of dissolved oxygen concentration results in stress, lower feeding response, disease susceptible and greater mortality rates of cultured species (Boyd and Hanson, 2010; Boyd et al., 2018). Hence, aeration becomes a necessity as it elevates the dissolved oxygen (DO) concentrations in the systems, ensures better fish productivity and maintaining overall fish health (Boyd and McNevin 2021; Ariadi et al., 2023; Ramesh et al., 2024). Aerators use in aquatic systems aids in maintaining the DO levels well above 5.0 mg/l, the optimum concentrations for aquacultural practices (Cheng et al., 2019).

Aeration of water bodies can be achieved via. injecting air directly into the water (Roy et al., 2017; Boyd et al., 2018; Roy et al., 2021a, b, c). The process of aeration increases the concentration of dissolved oxygen in the water bodies. This process is also effective for removal of harmful dissolved gases like CO2, H2S, and volatile organic compounds from the water bodies (Du et al., 2020). The two major techniques employed for aeration to improve DO levels of aquatic environments are natural aeration and artificial aeration (Tien et al., 2019; Nguyen et al., 2021). Increase of DO levels through natural aeration can be achieved through photosynthesis by aquatic plants and atmospheric diffusion on the water surface. Natural aeration also possesses a challenge since DO concentrations generally decrease at night, which can adversely impact the respiration and physiological processes of cultured organisms (Boyd 1998; Tanveer et al., 2018). With increasing adoption of intensive farming practices, natural aeration is not itself sufficient for maintaining DO levels for increasing aquaculture productivity. To address these issues artificial aerators have become widely used in aquaculture practices to compensate the greater demands of DO (Roy et al., 2021a, b, c).

Artificial aeration system enhances the air to water interaction interface area resulting in a greater amount of diffusion of O2 from the air into the water surface by stirring or agitating it. Artificial aeration systems are generally categorized into splash aerators and gravity aerators. They operate based on three fundamental mechanisms: (1) aeration achieved by projecting water into the air, i.e., paddle wheel aerators, vertical pumps, spiral aerators and pump sprayers; (2) aeration through the injection of air into water, i.e., propeller aspirators and diffuser aeration systems; and (3) aeration caused by water falling from a height, i.e., cascades, weirs and plate setups (Zhang et al., 2020; CIFA, 2024; AICRP on PEASEM, 2024, 2025). In aquaculture, aeration represents one of the most energy-intensive operations, contributing significantly to both high overhead costs and a larger ecological footprint (Jamroen, 2022). When aeration systems are poorly optimized, they lead to excessive power consumption and inconsistent oxygen levels throughout the water column. Such inefficiencies can jeopardize fish health, increase mortality rates and ultimately diminish total harvest yields (Bahri et al., 2019; Palya and MacPhee, 2023). These challenges highlight the need for more sustainable aeration technologies that optimize energy efficiency while ensuring adequate oxygenation. Therefore, a method for selecting aerators is crucial that are well-designed to provide a consistent and sufficient oxygen supply in intensive aquaculture systems while keeping energy expenditure costs at a minimum (Tien et al., 2019). 

A vertical aeration system is a mechanical or hydraulic arrangement designed to circulate water vertically above the pond surface. This system ideally set on the principle of mass transfer of atmospheric oxygen into pond surface to maintain adequate DO levels essential for aquatic organisms. Vertical aeration can be implemented as shower, cascade, trickling columns and other gravity-based aeration as it increases DO content, promotes water mixing and removes excess dissolved gases from the water. This process is widely adopted and practiced in both pond culture system and recirculating aquaculture systems. Cascade aerators have been identified as both effective and cost-efficient for most aquaculture practices (Singh, 2010; Roy et al., 2020b; AICRP on PEASEM, 2025). In these systems, water flows over a series of steps, breaking into droplets upon impact, which facilitates the entrainment of air from the atmosphere into the water (Roy et al., 2022). To enhance the aeration performance of cascade aerators, numerous studies and experiments have been conducted by researchers (Baylar et al., 2006; Baylar et al., 2010; Singh, 2010; Kumar et al., 2013; Roy et al., 2020a; AICRP on PEASEM, 2025). Shower aerators are designed with horizontally arranged showers fitted into pipelines positioned about 1.0 m above the water surface (AICRP on PEASEM, 2024; CIFA, 2024). A centrifugal pump is used to recirculate water by lifting it to a height and then it is released as fine spray droplets. These fine droplets augment the oxygen uptake from the atmosphere through adsorption. The aeration efficiency largely depends on the droplet surface area exposed to air, which is influenced by the shower nozzle size and the degree of water dispersion (Roshan et al., 2022). In both systems the principle of oxygen transfer is based on the dispersion of water droplets into air which is allowed to free-fall from a certain height, efficiently carries oxygen from atmosphere through the process of adsorption, resulting in the aeration of ponds. The flowing water increases its exposure to air as it spreads over a larger surface area that enables it to absorb oxygen before entering the tank (El-Zahaby and El-Gendy 2016).

This study provides a thorough evaluation of vertical aeration technologies, majorly focusing on their energy efficacy and proposing a process that integrates selection of aerator system, automation and the use of renewable sources of energy. It offers an extensive overview featuring practical executions and actual case studies. This work contributes to the creation of economical and environment friendly aeration systems by addressing both technological and operational challenges. The purpose of this review is to assess the energy efficiency of existing vertical and cascade aeration technologies. It presents a comparison based on cost-effectiveness, performance and applicability and identifies important factors that influence their use in aquaculture. The study additionally investigates its possible applications for sustainable aquaculture methods and provides an integrated model framework for future developments in vertical and cascade aeration systems. The implementation of such innovations is expected to possess lower operational and maintenance costs while addressing issues related to low dissolved oxygen levels, high volatile organic compound concentrations, nitrogenous waste accumulation and water stratification simultaneously. These innovations can serve as energy-efficient alternatives to different mechanical aerators for maintaining the optimum DO levels in aquaculture ponds.

Principles of aeration in aquaculture

Increased oxygenation is essential for preserving water quality because it makes it easier to get rid of dangerous gases like carbon dioxide (CO₂) and ammonia (NH₃), which may adversely affect fish survival, growth and health if they build up (Eze and Ajmal 2020; Roy et al., 2020a, 2022). Other benefits of aeration are preventing thermal stratification and maintaining uniform temperature distribution throughout the water column that is conducive for fish growth (Wongkiew, 2018; Silalahi et al., 2022). In ponds where extensive culture is practiced with a lower stocking density (

This review has comprehensively examined the role of artificial aeration systems in aquaculture, emphasizing their importance in maintaining dissolved oxygen levels for sustainable fish farming. By analyzing the principles, design characteristics, and performance of various aeration methods, the study underlines how technological innovations can address challenges related to oxygen depletion, water quality and energy efficiency in intensive aquaculture practices. It also highlights the scope for integrating cost-effective and environmentally sustainable approaches to strengthen aquaculture productivity.

Among the different systems reviewed, cascade aerators stand out for their simplicity, low cost, and reliability in improving water quality, while shower aeration systems demonstrate enhanced performance through design optimization and efficient oxygen transfer. Building upon these, vertical aeration towers integrating both cascade and shower principles are expected to provide superior efficiency by combining the strengths of both systems. Collectively, these advancements indicate that future research and development should focus on optimizing such integrated systems to ensure energy-efficient, sustainable and economically viable solutions for aquaculture ponds.

The cascade aerator is a commonly used alternative for the treatment of wastewater in place of conventional method. Used mostly after the initial stages of treatment, as a means of increasing the quantity of dissolved oxygen of the effluent water. Gases that are dissolved in effluent water can be reused (DO) or disposed of (H2S, CH4 and CO2) in a safe manner (Kumar et al., 2013). The turbulent movement of water as it descends the cascade steps creates an environment where there is a greater volume of water in contact with the atmosphere; this provides an efficient exchange of air and water, thus improving the oxygen transfer rate and assisting in removing volatile substances from the water, such as methane and chlorine gas, dissolved Fe and Mn, CO2, H2S, and volatile oils that may affect the taste and colour of the water (Toombes and Chanson 2005).

Although such aerators are commonly applied in wastewater treatment, their effectiveness in maintaining dissolved oxygen levels under real-world aquaculture conditions has received limited research attention. This study seeks to fill that knowledge gap by examining the properties of cascade aerators, aiming to improve understanding and provide guidance for optimal aeration practices in fish farming operations in practical field conditions. Choosing an appropriate model requires numerous considerations such as the purpose of the pond, characteristics and geometry of the pond, along with the financial costs related to the construction, operation and maintenance of the pond (Roy et al., 2020b). According to Roy et al. (2021a), gravity-based aerators are cost-effective, simple to operate and maintain, dependable and deliver adequate performance. Those are generally more effective for application in small ponds occupying less than 0.1 hectares.

Hence, the future thrust should be towards innovation of aeration devices mitigating this issue and should be effective for increasing pond sizes. Several noteworthy preliminary studies have already been carried out in this field. There remains potential to introduce new designs, packages, and practices into the existing framework to further strengthen the system and enhance its efficiency. Around three decades ago, a cascade-type bamboo aerator was demonstrated in a pond at ICAR-CIFA, Bhubaneswar. Some of the schematic diagrams mentioned in this study are currently being tested and evaluated in pond culture practices. At present, there is still scope to incorporate additional cost-effective aeration techniques and where necessary, refine the existing methods to achieve improved aeration in ponds.

The developed cascade aerator significantly improved water quality in fish ponds by enhancing oxygen transfer, achieving an overall transfer coefficient of 5.15–8.21 hr⁻¹, a standard aeration efficiency of 0.11–0.21 kg O₂/kW/hr, and a transfer rate of 0.04–0.08 kg O₂/hr (Kumar et al., 2013). This efficient, low-cost system offers a sustainable solution to boost fish stock density for low-income farmers. The shower aeration system (SAS) achieved optimum performance at a 10 mm radius of curvature, yielding (SAE) of 1.4429 kg O₂/kWh and a normalized SAE (NDSAE) of 15.914 × 10⁶ (Roshan et al., 2022). Such results highlight the importance of geometric optimization in enhancing system efficiency for effective water aeration. It should be hypothesized that vertical aeration towers, integrating both gravity-driven cascade and shower aeration principles, will achieve superior oxygen transfer efficiency compared to conventional systems. By combining the strengths of cascade and shower aeration, the system is expected to deliver higher SAE values, making it a more effective and sustainable solution for enhancing fish pond productivity.

Integrating innovative aeration technologies with renewable energy sources offers a cost-effective approach to reducing aquaculture’s reliance on conventional electricity generation. Among the various renewable options, solar energy is the most widely utilized for pond aeration (Jamroen, 2022). Solar panels can be installed along pond banks or mounted on floating platforms to supply the power required for aeration systems, minimizing dependence on the local electrical grid (Jamroen, 2022; Chudasama et al., 2023; Nugraha, 2025). Sustaining high water quality in aquaculture while enhancing energy efficiency increasingly relies on the integration of sensors and automated control systems within aeration management. Modern aquaculture aeration systems frequently use dissolved oxygen (DO) sensors and other real-time monitoring technologies to track critical water quality parameters and adjust aeration as needed, minimizing energy waste and promoting optimal oxygen levels for cultured species (Uken and Getachew 2023; Flores-Iwasaki et al., 2025). By linking these sensors to Internet of Things (IoT)-based automated controls, aerators can be operated only when DO thresholds are not met, reducing unnecessary power consumption and improving overall energy efficiency (Nugraha, 2025). Such sensor-driven automation not only enhances water quality and aquatic health, but also supports environmental sustainability by lowering operational costs and reducing resource use (Uken and Getachew 2023; Flores-Iwasaki et al., 2025). Understanding the components of aeration systems including real-time DO sensing, smart controllers, and adaptive feedback loops is essential for selecting strategies that boost both productivity and energy efficiency, positioning the aquaculture industry to address future aeration challenges as sustainable resource management technologies continue to advance.

Future research should emphasize developing methods that make these advancements more accessible and cost-effective for a wider range of users. This study represents a significant step toward enhancing aeration practices in aquaculture and contributes to the sustainable advancement of the aquaculture industry. Henceforth, the current study hypothesizes an optimized cascade aeration can serve as an efficient aerator substituting the mechanical aeration producing higher efficiency than the latter. Testing of the hypothesis through pond-scale trails and simulations will be decisive for the validation of cascade aeration as a scalable solution for the sustainable aquaculture practices.

Bikash C. Mohapatra and Sambid Mohanty  (2026). Cascade and Vertical Aeration Systems in Aquaculture: Current Status, Design Hypotheses and Future Needs. Biological Forum, 18(1): 01-12.