Paul B. Brown

Revolving Algal Biofilm (RAB) reactors offer a space-efficient and low-energy method for producing algal biomass by cultivating algae on a rotating belt surface. Their unique biofilm-based attached-growth mode simplifies harvesting and enhances nutrient recovery by maintaining continuous contact with nutrient-rich water. Despite these advantages, the application of RAB systems in aquaponic configurations has received limited attention, especially in relation to reactor design, system performance, nutrient recycling, and algal quality. This study investigated the integration of Chlorella vulgaris cultivation using a RAB system within a coupled aquaponics configuration, compared alongside a decoupled suspended-algal system and a conventional fish–plant control. Over a 35-day period, a total of nine independent systems were monitored to evaluate algal biomass productivity and nutritional composition, as well as fish growth and lettuce yield. Fish growth and survival, and lettuce yield did not differ significantly across treatments demonstrating that algal integration, whether coupled or decoupled, did not compromise primary aquaponic outputs. RAB-derived biomass exhibited higher crude protein and lipid than suspended decoupled algae biomass, along with enriched essential and non-essential amino acids (e.g., lysine and methionine) and greater proportions of long-chain polyunsaturated fatty acids (e.g., ARA, EPA, DHA). Overall, the coupled RAB system enhanced algal biomass productivity per unit surface area, and biomass quality without negatively impacting fish growth or plant yield. RAB-coupled aquaponics thus offers a practical route to produce high-value algal biomass while maintaining system performance, supporting circular nutrient recovery and diversified outputs.

Revolving Algal Biofilm (RAB) reactors offer a space-efficient and low-energy method for producing algal biomass by cultivating algae on a rotating belt surface. Their unique biofilm-based attached-growth mode simplifies harvesting and enhances nutrient recovery by maintaining continuous contact with nutrient-rich water. Despite these advantages, the application of RAB systems in aquaponic configurations has received limited attention, especially in relation to reactor design, system performance, nutrient recycling, and algal quality. This study investigated the integration of Chlorella vulgaris cultivation using a RAB system within a coupled aquaponics configuration, compared alongside a decoupled suspended-algal system and a conventional fish–plant control. Over a 35-day period, a total of nine independent systems were monitored to evaluate algal biomass productivity and nutritional composition, as well as fish growth and lettuce yield. Fish growth and survival, and lettuce yield did not differ significantly across treatments demonstrating that algal integration, whether coupled or decoupled, did not compromise primary aquaponic outputs. RAB-derived biomass exhibited higher crude protein and lipid than suspended decoupled algae biomass, along with enriched essential and non-essential amino acids (e.g., lysine and methionine) and greater proportions of long-chain polyunsaturated fatty acids (e.g., ARA, EPA, DHA). Overall, the coupled RAB system enhanced algal biomass productivity per unit surface area, and biomass quality without negatively impacting fish growth or plant yield. RAB-coupled aquaponics thus offers a practical route to produce high-value algal biomass while maintaining system performance, supporting circular nutrient recovery and diversified outputs.

Aquaculture sludge (AS), rich in nutrients, can pose environmental risks such as eutrophication, threatening aquatic ecosystems and water quality if not properly managed. However, AS can also be used as a feedstock for bioenergy production. This study investigated bioenergy (methane) production from AS and dairy manure (DM) under anaerobic codigestion using the biochemical methane potential test. Results showed that anaerobic codigestion of DM and AS produced higher methane production compared with their individual monodigestion. The DM:AS ratios of 50:50, 30:70, and 10:90 showed synergistic effects, with codigestion performance indices of 1.2, 1.3, and 1.5, respectively. A DM:AS ratio of 10:90 provided the highest methane production of 341.80 mL g⁻¹ volatile solids, being 65% and 52% greater than those from monodigestion of these two feedstocks, respectively. A hydraulic retention time of 16 days was found optimum, attaining 90% of the cumulative methane production. The experimental data of methane production fitted perfectly with the superimposed model, reflecting contribution from both readily degradable and harder fractions of the feedstock mix. These findings present an approach to effective valorization and management of the nutrient‐rich AS through enhanced energy recovery and promote sustainability in the aquaculture industry.

Tilapia is a widely cultured species native to Africa; these fish are prolific breeders and constitute an economically important fish species supplying higher-quality protein. To meet the global food demand and achieve the UN’s Sustainable Developmental Goals (SDG), the aquaculture industry has conceived of productive solutions with the potential for adaptability, palatability, and profitability. Tilapia may play a vital role with respect to the possibility for sustainability in the nutrition and aquaculture sectors. India contributes to the promotion of aquacultural practices through a structural framework focused on agricultural, environmental, geographical, and socio-economic factors that provide opportunities for tilapia farming. Globally, the Indian aquaculture sector is currently the second largest in terms of aquacultural production but is moving toward different species that meet SDG and facilitate international marketing opportunities. The farming of aquacultural species with innovative technology constitutes an efficient use of resources. Productive research on feeding, disease management, construction, and layout helps overcome the challenges faced in aquaculture. These focused and sustained factors of the aquaculture industry offer a latent contribution to global food security. This review reports on the state of the art, the challenges regarding tilapia aquaculture in India, and the Indian government’s schemes, missions, subsidies, projects and funding related to tilapia production.

PH is the major issue that concerns all producers in aquaponics, as the main three organisms (aquatic animal, plant, and microbes) have different preferences. Additional C is a potential approach to amend the growing environment and improve shrimp and plant growth, and microbe establishment. Aquaponics under saline conditions has, however, not been studied in detail in regard to the effect of pH and additional C. In this study, we evaluate the impact of pH and additional C on the growth of Pacific whiteleg shrimp and five edible plants (three halophytes and two glycophytes) in marine aquaponic systems using nutrient film technique (NFT). The results indicated that plants grow better in both pH 6.5 treatments; however, additional C improved the growth in pH 7.5 + C treatment and had similar yield to lower pH treatments. The results indicated both pH and additional C had little impact on shrimp growth. In conclusion, adding C can be a practical solution to the pH conundrum for marine aquaponics. Appling additional C was suggested for the operation of marine aquaponic food production system when the pH is high.

PH is the major factor that makes producers in aquaponics frustrated, since the main three organisms (aquatic animal, plant, and microbes) in the system with different preferences. Yet, amending the growing environment with additional C is a potential method to improve the growth of shrimp and plants as well as the establishment of microbe. A detailed study of the effects of pH and additional C on aquaponics under saline conditions has not been investigated. In this study, the effect of pH and additional C on the growth performance of shrimp (Litopenaeus vannamei) and five edible plants in marine aquaponic systems using the nutrient film technique (NFT) was evaluated. The results indicated that at both pH 6.5 treatments, plants grew better; nevertheless, the growth performance of plants in pH 7.5 with additional C was improved and showed a similar yield to lower pH treatments. On the other hand, shrimp growth was little affected by pH and additional C. A higher impact of imbalanced ionic composition on shrimp performance may have contributed to this trend. Hence, we suggest that only if the ionic composition is managed can make RO water a suitable source of water for shrimp-based aquaponic. In spite of this, more research is required.

Formulated diets for animals is the primary source of nutrients in aquaponic systems that need to maintain beneficial bacteria as well as for plants. Dietary protein is one of the expensive macronutrients in fish diets, especially when fishmeal is used, and it is the source of nitrogen (N) for other biotic components. Biofloc has the potential to serve as the supplement diet for shrimp and reduce the need of expensive protein. However, it is not clear if low dietary protein will be adequate to support the three organisms (animals, plants, and bacteria) in an aquaponic system operated with biofloc technology. The aim of the present study was to investigate the effect of shrimp feed with different protein concentrations (30, 35, or 40%) on water quality and the growth performance of Pacific whiteleg shrimp (Litopenaeus vannamei) and three edible halophytic plants (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) in biofloc-based marine aquaponics. The experiment was conducted for 12 weeks, the plants were harvested and seedlings transplanted every 4 weeks. Dietary protein content did not influence shrimp growth in the current study, indicating that feeds with lower protein concentrations can be used in biofloc-based marine aquaponic systems. During the early and mid-stages of cultivation, plants grew better when supplied diets with higher protein concentration, whereas no differences were observed for later harvests. Hence, for maximum production with mature systems or in the scenario of high concentration of nitrate, providing a higher protein concentration feed in the early stages of system start-up, and switching to a lower protein concentration feed in later stages of cultivation was recommended.

Integrated aquaponic food production systems are capable of producing more food on less land using less water than conventional food systems, and marine systems offer the potential of conserving freshwater resources. However, there have been few evaluations of species combinations or operational parameters in marine aquaponics. The goal of this experiment was evaluation of stocking density ratio of Pacific whiteleg shrimp (Litopenaeus vannamei) to three edible halophytes (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) with two C/N ratios in a 3 × 2 factorial design. There were three stocking density ratios (shrimp: plant), 2:1, 3:1, and 5:1; and two C/N ratios, 12 and 15. The results indicated that stocking density ratio exerted a significant impact on shrimp growth. Shrimp reared in 2:1 and 3:1 treatments had better growth performance. In contrast, plants were affected by both stocking density ratio and C/N ratio. Halophytes grown in stocking density ratios of 3:1 and 5:1 with a C/N ratio of 15 had better growth performance and nutrient content. The concentrations of TAN and NO₂^– were below 0.2 mg/L throughout the experiment, including the higher stocking density ratio treatments. In conclusion, the stocking density ratio of 3:1 with a C/N ratio of 15 was suggested as the optimal condition for the operation of marine aquaponics in which whiteleg shrimp and the three halophytes are target crops.