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The aquaculture industry is an efficient edible protein producer and grows faster than any other food sector. Therefore, it requires enormous amounts of fish feed. Fish feed directly affects the quality of produced fish, potential health benefits, and cost. Fish meal (FM), fis oil (FO), and plant-based supplements, predominantly used in fish feed, face challenges of low availability, low nutritional value, and high cost. The cost associated with aquaculture feed represents 40-75% of aquaculture production cost and one of the key market drivers for the thriving aquaculture industry. Microalgae are a primary producer in aquatic food chains. Microalgae are expanding continuously in renewable energy, pharmaceutical pigment, wastewater treatment, food, and feed industries. Major components of microalgal biomass are proteins with essential amino acids, lipids with polyunsaturated fatty acids (PUFA), carbohydrates, pigments, and other bioactive compounds. Thus, microalgae can be used as an essential, viable, and alternative feed ingredient in aquaculture feed. In recent times, live algae culture, whole algae, and lipid-extracted algae (LEA) have been tested in fish feed for growth, physiological activity, and nutritional value. The present review discusses the potential application of microalgae in aquaculture feed, its mode of application, nutritional value, and possible replacement of conventional feed ingredients, and disadvantages of plant-based feed. The review also focuses on integrated processes such as algae cultivation in aquaculture wastewater, aquaponics systems, challenges, and future prospects of using microalgae in the aquafeed industry.

This experimental investigation of a laboratory scale aquaponic system included testing of a biofilter with basil plant as the biofilter part on aquaculture water quality. Irridescent shark was selected as aquaculture species. The biofilter consist of natural biomaterials such as coconut husk, coco peat, and coarse aggregates. The experiment was carried out for three short water recirculation durations of 2, 3, and 4 h/day. The influent and effluent ammonia NH3, total ammonia nitrogen (TAN), nitrites NO2 and nitrates NO3 levels were measured and analysed. The results showed that the biofilter effectively removed NH3 (65 - 71 %), TAN (34 - 58 %), and NO2 (60 - 67 %) from the aquaculture water. The dissolved oxygen (DO) levels were maintained between 3 - 7.0 mg/l during all the recirculation durations. The significance of water recirculation period was assessed by calculating the differences between the means of water quality parameters with a statistical test named one-way analysis of variance (ANNOVA) with significant level P taken as 5 %, i.e., P ≤ 0.5. The effluent mean NH3 levels 0.030 mg/l, 0.033 mg/l, and 0.022 mg/l exhibited significant difference at 4 h/d periods while effluent TAN levels 0.81, 0.77, and 0.77 showed no difference with varying periods.

Aquaponic is a combination of aquaculture and hydroponic plants in the recirculation system. The aquaponic system has a constraint in the form of ammonia which is produced by fish metabolism. In order to increase the productivity of fish and plants in aquaponics, an approach by integrating filters and biofilter could be used to reduce ammonia waste. The aim of this research was to study the use of zeolite, charcoal, and water spinach as components of integrated filters to reduce ammonia concentration in an aquaponic system. This research was conducted for four weeks with three repetitions of water sampling sourced from pond, filters, and output. The results of this study indicated that the use of combination of zeolite, charcoal and water spinach as componentof integrated filters can reduce ammonia throughout the research period.

Raised bed production trials were conducted to evaluate the effectiveness of effluent from a biofloc-style recirculating aquaculture system producing nile tilapia (Oreochromis niloticus) as nutrient-rich irrigation water for fall ‘Celebrity’ tomato (Solanum lycopersicum) production. The objective of this study was to provide baseline vegetable production data and justification for using aquaculture effluent as a water and nutrient resource. The experiment was a split-plot, randomized block design with three treatments: aquaculture effluent, granular fertilizer, and fertigation. Tomato seeds were sown in June, transplanted in August, and grown until Oct. 2019 in nine replicated raised beds. Conventional field tomato production practices were followed throughout the trial, and data were collected for tomato fruit yield, market quality, size, leaf greenness (SPAD), and foliar nutrient analysis. Fruit yield was similar between fertigated and aquaculture effluent treatments, with granular fertilizer resulting in yield that was significantly lower (P ≤ 0.033). SPAD measurements were similar among treatments. All nutrients met or exceeded sufficiency ranges. Foliar nutrient analysis revealed no significant difference for nitrogen, phosphorus, potassium, magnesium, calcium, boron, zinc, manganese, and iron among treatments. Sulfur and copper levels were significantly lower (P < 0.05) with aquaculture effluent treatment as compared with the granular and fertigated treatments. Overall, tomato production using aquaculture effluent as a water and nutrient supplement produced similar yields to commercial practices, making it potentially viable for producers.

Aquaculture has experienced a burgeoning growth worldwide in the last decade resulting in nearly 50% of seafood originating from aquaculture farms. However, there are less studies on the utilization of the manure produced by aquatic organisms in comparison to warm-blooded livestock. Aquaponics offers more efficient utilization of nutrients and can reduce the operational costs in aquaculture. This paper presents the results of a study to identify the optimal settings to digest fish manure through a microbial-assisted aerobic bioprocess, using endogenous heterotrophic and nitrifying bacteria. The effects of pH (5.5, 6.0 and 6.5), temperature (30, 35 and 40 °C) and duration (1–30 days) on kinetics of nitrogen mineralization were investigated and compared to a control bioreactor (carried out without pH adjustment). The mineralization dynamics for all pH-controlled bioreactors revealed that only ammonification occurred. No nitrification was observed for all three-temperature conditions and throughout the entire bioprocessing period. The mineralization process in the control bioreactor, on the other hand, followed the typical non-inhibited nitrogen mineralization (i.e., release of ammonium followed by oxidation into nitrate). However, nitrate was only observed at temperatures

Operation and effluent treatment costs are limiting factors for the success of recirculating aquaculture systems (RAS) in meeting seafood demand in the United States. Adopting a capture-and-reuse waste management model similar to terrestrial agriculture farmers would allow RAS farmers to monetize effluent and offset production costs. The moisture content and nutrient profile of RAS effluent makes it a potential option for use as a hydroponic fertilizer. Treatment of RAS waste is needed to mineralize particulate-bound nutrients before becoming a viable hydroponic nutrient solution. Anaerobic treatment (AT), a method used by municipal and agricultural waste treatment facilities to reduce total solids, has been shown to successfully mineralize particulate-bound nutrients from RAS effluent. Continuously mixed anaerobic batch bioreactors were used to evaluate the degree to which AT may mineralize particulate-bound nutrients in solid RAS waste. Concentrations of twelve different macro- and micro-nutrients were analyzed in the waste before and after treatment. Effluent samples were analyzed to determine the fraction of each nutrient in the solid and aqueous forms. This study showed that AT is an effective method to mineralize particulate-bound nutrients in RAS effluent and the mineralization rate data may be used to design a pilot-scaled flow-through RAS effluent treatment system.

Aquaponics combine the production of fish and plants in a sustainable way due to the double use of water and nutrients. Compared to conventional single recirculation aquaponic systems (SRAPS), the double recirculation aquaponic systems (DRAPS) are improved by the combination of two separate recirculating systems: the recirculating aquaculture system (RAS) for fish rearing and a closed hydroponic cycle for plant production. Both systems are connected in one direction to transfer the nutrient rich fish waste water to the hydroponic unit. The unidirectional connection of both systems allows the optimisation of fish waste water for plant growth by addition of mineral fertilizer without negative effects on fish rearing. DRAPS is a relative new approach and information about the functionality and successful use are rare. Therefore, more research on DRAPS is necessary. The present study was focused on different growth and production parameters of tomatoes produced in DRAPS compared to those produced in conventional hydroponics. Investigations during an annual production in 2015 showed that tomatoes produced in DRAPS have a comparable plant growth and development as obtained for conventional hydroponics. Even the fruit quantity and the fruit quality, including nutrient contents, were similar in both production systems.

Aquaponics is considered as a promising approach to mass produce both fish meat and vegetable at high rates without discharge pollutants. A novel aquaponics system is proposed to control water quality and enhance nutrition efficiency with high rate immobilized biofilm units, including mass-bio system (MBS) and fiber biofilter (FB), installed between upstream hydroponics units, which are composed of the media filled beds (MFD) and nutrient film technique (NFT), and downstream aquaculture unit for fish rearing. A pilot test was conducted over 130 d to characterize the performance of proposed system which converted residual nutrients from aquaculture unit into ammonium and nitrate at balanced ratio for aquatic plant growth and then removed residual ammonium or/and nitrite to ensue recycled water quality for fish rearing. The kinetics of organic matter removal and nutrient conversion in hydroponics unit and immobilized biofilm units were determined via batch assays over 24 h in the system. The estimated daily pollutant increments for TAN, NO2−-N, NO3−-N, TN, DTP and TOC in the system were 0.28, 0.17, 0.20, 0.64, 0.56 and 2.19 mg/L, respectively. The results demonstrated that total ammonia nitrogen (TAN), nitrite (NO2−-N), nitrate (NO3−-N), total nitrogen (TN), dissolved total phosphorus (DTP) and total organic carbon (TOC) were maintained at low levels in the system for a long-term. Aquatic plants in MFD and NFT contributed to the removal of TAN, NO2−-N, NO3−-N, TN and DTP. The removal efficiencies of MFD versus NFT for TAN were 71.4% vs 43.5% for TAN and 62.5% vs 52.3% for DTP. MBS and FB performed the removal of TAN, NO2−-N and TOC. The 24 h removal efficiencies of TAN, NO2−-N and TOC were 71.8%, 58.5% and 3.7% for MBS and 15.7%, 7.7% and 27.2% for FB.

Aquaponics is the integration of recirculating aquaculture and hydroponic systems which is considered to be an innovative, eco-friendly and sustainable food production technology. In this study, a special design of hydroponic biofilter that integrated constructed wetlands and floating-raft rice hydroponics was constructed to treat the nutrient rich effluents from the intensive fishpond and to establish an aquaponic system on pond scale. The treatment efficiencies and food production potential of the new rice hydroponic biofilter was evaluated after determining the key operating parameters. As the results, overall nutrient removal efficiency was optimized at hydraulic load rate (HLR) of 0.58 m.d−1 and air-to-water ratio of 2:1. The average removal efficiencies of total ammonia nitrogen (TAN), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (CODMn) from fishpond wastewater were in the range of 33.75–34.31%, 59.21–64.53%, 68.43–73.75% and 71.66–74.37%, respectively. Meanwhile, hydroponic rice grew well in the biofilter and gained a yield of 7 127 kg.ha−1. These results probably implied that the novel rice hydroponic biofilter exhibited efficient effluent treatment and presented as a viable alternative for the food production in a pond-scale aquaponics recirculating system.

There is a recognized need for mineralizing aquaculture-derived sludge in aquaponics systems in order to reduce waste production. Many recent studies of aquacultural waste treatment have focused only the production of biogas as opposed to the potential for mineralization of nutrient-rich sludge. Upflow anaerobic sludge blanket (UASB) reactors provide one possible solution for breaking down sludge into bioavailable nutrients that can subsequently be delivered to plants. As such, this study examines the mineralization performance of sequential UASB reactors that are designed with an expanded granular sludge bed (EGSB) and compared to standard aerobic and anaerobic batch reactors. Results of our experiments demonstrate that only chemical oxygen demand reduction is significantly different. An unexpected drop in pH of one of the three reactor systems revealed that a pH below 6 was able to significantly increase the mineralization and mobilization of nutrients. Approximately 25% of phosphorus, potassium, and calcium could also be recovered from the sludge under lower pH conditions, as compared to the mineralization performance of standard UASB reactors running at a higher pH. However, the opposite effect was observed with respect to organic sludge reduction, where diminished performance was observed in the low-pH reactor. The current study implies that anaerobic reactors operating at low pH can potentially contribute towards improved nutrient recovery in multi-loop aquaponics systems and reduction of additive agents for pH control of the hydroponic subsystem.

The need to expand marine fish production and improve the economic viability and sustainability of recirculating aquaculture systems led to the development of a zero-discharge, marine aquaponic system. In this study, water treatment capacity, nutrient cycling, and biomass production were evaluated in a prototype, commercial-scale marine aquaponic system that included a moving bed bioreactor (MBBR) for nitrification, a sand filter for solids removal and denitrification, and hydroponic plant beds. Red drum (Sciaenops ocellatus), two species of edible halophytes sea purslane (Sesuvium portulacastrum) and saltwort (Batis maritima), and organic solids, were successfully produced over a 9-month period. Extensive analysis of solids, organic matter, and nutrients (nitrogen and phosphorous) in water and plant biomass was used to develop detailed mass balances on the system. Simultaneous operation of the moving bed bioreactor (MBBR) and plant beds resulted in high ammonia removal rates, allowing the system to support a high fish biomass density (38.8 kg/m3). Passive denitrification was the main nitrate removal mechanism, contributing to approximately 59% of aqueous nitrogen removal. Conversion of a sand filter to a side-stream denitrification reactor resulted in removal of 17% of the daily aqueous nitrogen load and prevented nitrate accumulation in the system. In addition to fish and edible halophyte production, 34 kg of organic solids were harvested from the sand filter and provided to a commercial nursery that used the solids as a fertilizer. This study demonstrates that marine aquaponics is an effective way to simultaneously produce marine fish, edible halophytes, and fertilizer. Addition of biological MBBR and a denitrifying sand filter was shown to be beneficial in situations where there are space limitations for plant growth, unexpected plant losses, or to support high densities of fish.

Aquaponics plant waste, such as the non-edible parts of many vegetable crops, can be a source of environmental pollution, while its treatment might cause an economic burden. Therefore, efficient use of this waste would be advantageous. This study aimed at investigating anaerobic digestion of aquqponic lettuce waste to recover nutrients and energy through biogas production. A 700 L commercial anaerobic system was used to treat lettuce wastes from an aquaponic farming system that operated under desert climate and steady-state conditions. Digestion efficiency of the lettuce waste was 90.1% by weight, producing a maximum biogas volume of 0.65 m3/kg dry weight per day. Biogas composition contained on average 59.2% methane and 38.9% CO2 with only negligible hydrogen sulfide content. Moreover, the supernatant from the anaerobic digester contained elevated nutrient concentrations (N, P, K, Ca, and Fe), which can potentially be used onsite as a fertilizer. Onsite anaerobic digestion of lettuce plant waste from the aquaponic system under summer desert conditions is demonstrated for the first time to efficiently reduce pollution burden, produce high-quality biogas, and recover nutrients.

In the aquaponic system, fishpond water contains ammonia derived from the rest of the feed, fish feces and fish metabolism. Ammonia at high concentrations can be deadly poisonous fish, reduced dissolve oxygen content and pH, increase biological oxygen demand and chemical oxygen demand. This study aims to determine the ability of biochar/CuFe2O4 as a media filter in the aquaponic system to reduce the concentration of inorganic ammonia such as ammonia (NH3), nitrate (NO3) and nitrite (NO2) in gourami pond water with bell pepper plants. It also measured the growth of Gourami and bell pepper growth. The results showed that the aquaponic system equipped with media filter biochar/CuFe2O4 was able to reduce the ammonia content by 91%, increase the growth of Gourami and bell pepper plants compared to the unfiltered aquaponic system which was only able to reduce ammonia by 35%.

Aquaponics is a cultivation technology that combines fish farming with plants. The degree of acidity (pH) and total dissolved solids (TDS) must be monitored for optimal fish and vegetable growth. In this research, a monitoring system was designed for pH and TDS in aquaponics and automation of fish feeding based on scheduling and level of need. Monitoring of pH and TDS as well as automation of fish feeding is done through an Android-based application. Fish feeding is carried out according to a schedule with a specified feed weight. The monitoring system for pH and TDS are carried out in real-time. The sensors used in this research are a pH sensor to measure pH values and an analog TDS sensor to measure total TDS. The communication system used is based on IoT technology. Based on the test results, it is found that the average difference between the readings of the pH sensor and the pH meter is 0.66% and the average difference between the readings of the TDS sensor and the TDS meter is 2.588%. The system has been able to provide fish feed according to a set schedule automatically and with a feed weight as needed with an error rate of only 1%.

Aquaponics is an intensive sustainable food production system that combines aquaculture and hydroponics, in which fish and plants grow together symbiotically. In an aquaponic unit, the effluent rich nutrients derived from nitrogenous waste excreted from fish, fish feed and decomposing organic matter,fertilizes hydroponic beds providing essential nutrients for plant growth. Simplified raft aquaponic system vary greatly in design and construction, but perform all key functions of plant and fish production, removal of suspended solids and bacterial nitrification. All life forms require nitrogen as an integral part of proteins and nucleic acids, therefore all living organisms are involved in the nitrogen cycle. This process is primarily accomplished by two groups of autotrophic nitrifying bacteria that can build organic molecules and utilize CO2 as the carbon source for biosynthesis and oxidation of nitrogen compounds as the energy source. Abroad range of major parameters and factors affecting bacterial growth has been studied in this paper which are essential for nitrification, that include healthy biofilter with appropriate water conditions like, water temperature, pH, dissolved oxygen (DO), total nitrogen concentrations. Characterization and identification of bacterial populations in an aquaponics system has been carried out by cultivation-dependant techniques and traditional methods of analyzing microbial communities using standard light microscopy.

Highlights • Non-conductive filling material brought insufficient and uncontrollable N removal. • Polarized conductive filling material provided limited but controllable N removal. • Mix of non-conductive and polarized conductive material were the most active. • The electrified biotrickling filter met the N standards, closing aquaponics loop., This work aimed to study the electrification of biotrickling filters by means of Microbial electrochemical technologies (MET) to develop an easy-to-assemble and easy-to-use MET for nitrogen removal without external aeration nor addition of chemicals. Four different designs were tested. The highest ammonium and nitrate removal rates (94 gN·m−3·d−1 and 43 gN·m−3·d−1, respectively) were reached by combining an aerobic zone with an electrified anoxic zone. The standards of effluent quality suitable for hydroponics were met at low energy cost (8.3 × 10−2 kWh·gN−1). Electrified biotrickling filters are a promising alternative for aquaponics and a potential treatment for organic carbon-deficient ammonium-contaminated waters.

Aquaponics is a significant wastewater treatment system which refers to the combination of conventional aquaculture (raising aquatic organism) with hydroponics (cultivating plants in water) in a symbiotic environment. This system has a high ability in removing nutrients compared to conventional methods because it is a natural and environmentally friendly system (aquaponics). The current chapter aimed to review the possible application of aquaponics system to treat fresh market wastewater with the intention to highlight the mechanism of phytoremediation occurs in aquaponic system. The literature revealed that aquaponic system was able to remove nutrients in terms of nitrogen and phosphorus.

The increase of global population causes rising food demand and concomittantly scarcity of resources. These facts including global warming need the further development of resource-efficient food production systems such as double recirculating aquaponic systems (DRAPS). This recent technology is suitable for intensive food production with minimal resource input and maximal reduction of emissions. In DRAPS fish water can be adjusted for plant growth (pH, nutrients) and both species are produced separately under optimum conditions. Primarily, the present study was conducted to investigate the improvement of DRAPS by implementation of an innovative suction filter device and, in addition, it is the first empiric investigation of combined African catfish (Clarias gariepinus) and tomato (Solanum lycopersicum L., cv. Pureza) production in DRAPS. Due to an immense loss of nitrogen caused by the primary sedimentation unit as connection between the fish and plant parts, the original DRAPS was modified by a new developed suction filter device to remove solid particles at minimal nitrogen loss. The nitrogen loss was significantly reduced by that system modification (≈43%) and thus resulted in a quite large reduction of greenhouse gas emissions due to the reduced need for manufacturing of nitrogen fertiliser. The combined production of African catfish and tomatoes in aquaponics revealed similar fruit yields of tomatoes as for the control using artificial fertiliser, while the overall fertiliser use in aquaponics was about 13.2–77.7% lower. However, fertiliser saving was highest after modification and replacement of the sedimentation unit by the new suction device. In addition, in comparison to already existing aquaponic systems, the total biomass output was significantly increased. The results were evaluated under consideration of intensive crop production in hydroponics.

Aquaponics is an integrated system in which the water containing fish waste is used as a nutrient source for plant production in a closed recirculation system. In this study, tilapia (Oreochromis niloticus) and pak choi (Brassica chinensis) culture was tested using two techniques: 1) Root floating (RAFT), and 2) Dynamic root floating (DRFT). Water quality parameters, total ammonia nitrogen, nitrate nitrogen, nitrite nitrogen and phosphate were measured. At the end of the experiment, fish and plants were weighed and the required electric power consumption was calculated. There was no significant difference observed between the effect of each treatment group on either tilapia or pak choi production. Tilapia productivity was 1.69 ± 0.22 kg/m3 and 1.71 ± 0.23 kg/m3 and pak choi yield was 7.43 ± 1.23kg/m2 and 7.32 ± 0.76 kg/m2 for the RAFT and DRFT, respectively. Water quality parameters were within the recommended range for the tilapia culture while pH and conductivity were out of range for the pak choi culture; nevertheless, plant production was good. Total ammonia nitrogen and nitrite nitrogen did not reach concentrations that could impede tilapia growth. The DRFT allows the elimination of active aeration in hydroponic systems for tilapia and pak choi production during most of the cycle, reducing the electric power consumption to 10.3% and electricity costs to 11.4% by using a nature-based solution.

The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater. This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days. The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m−2) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m−2 day−1). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m−2 day−1) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.

The success of a culture depends on the quantity and quality of water used in fish culture without water exchange, the concentration of aquaculture waste such as ammonia (NH3) will increase very rapidly and is toxic to the cultivated organism. One of the innovations applied in fish farming is integrating plants through an aquaponics system. This study aims to determine the effect of using a settling tub in reducing ammonia waste (NH3) and growth in tilapia aquaculture using an aquaponic tidal system. The size of the initial tilapia seeds used is 3-4 cm. There are two treatments used, without settling tub (A) and addition of settling tub (B) with three replications. However, the results showed no significant differences (P>0.05) between treatments for all parameters observed. It is necessary to carry out further research on different fish and plants to see the optimization in reducing ammonia waste (NH3).

Aquaponics system is an innovative idea which combined both aquaculture and hydroponics systems. In this study performance of four different types of water treatment technique was investigated in cocopeat media filled grow bed aquaponics system. The techniques that had been investigated were mechanical filter, biological filter, combination of both mechanical and biological filters and grow media (cocopeat) itself as filtration media. The effectiveness these techniques were assessed through (i) water quality and nutrients level of circulated water and (ii) growth rates of plant (Gynura procumbens) and Red Nile Tilapia fish (Oreochromis niloticus) The (i) water quality (pH, temperature, total suspended solid and dissolved oxygen) (ii) nutrient level (ammonia, nitrite, nitrate) and (iii) grow rates of plant and fish were weekly measured for this study. The results revealed that cocopeat media filled grow bed only was insufficient to act as water treatment unit in the aquaponics system studied. The aquaponics system required at least a biological or mechanical filter to produce acceptable yields of fish and plant. For the long term, the combination of axial flow and biofilter with superlative ratio was suggested in order to produce the best performance of parameters studied. This integrated technique was able to maintain the water quality within the tolerance limit of fish besides supplying enough amount nutrients (especially nitrate) for the plant growth and easier maintenance work in terms of cleaning and disposal of sludge.

One pilot-scale portable Nutrient Film Technique (NFT) aquaponic system has been designed, developed, and tested at ICAR-CIFA, Bhubaneswar for a period of 90 days (October to December 2018) to study the efficiency of the new design. The experimental setup has three separate units, each consisting of four major components, such as Fibreglass Reinforced Plastic (FRP) round fish culture tank (o2.15 × 0.9 m) with operational capacity 2800 L, biofilter unit made up of Polypropylene (PP) of 100 L capacity, FRP rectangular hydroponics tank (4 × 0.9 × 0.35 m) having 2.64 m2 plantation area and High-density Polyethylene (HDPE) sump (o0.6 × 0.7 m) of 200 L capacity. Implementation of custom designed and calibrated automatic water recirculation system gives an average flow rate of 94.7 L/h for continuous flow of nutrients from fish culture tank to hydroponics tank. The designed system harnesses gravity flow in 75 % of the cycle. For performance assessment, the system was initially stocked with 54 numbers of fish fry/m3 (153.7 g/m3) of pangas (Pangasius hypophthalmus) in culture tank and 27 marigold (Tagetes erecta) plants/m2 in hydroponics tank. Length and weight gain of fish were by 77.04 % and 397.2 % from initial, respectively, and marigold plant harvested 107 number of flowers/m2. The Total Ammoniacal Nitrogen (TAN) reduction in biofilter was found to be 61.97 %.

The recovery of nutrients from residual fish sludge in aquaponics could achieve zero solid waste discharge and supplement additional nutrients to hydroponics, thus yielding environmental and economic benefits. In this study, novel biological aerated filters (BAFs) with ceramsite plus different lignocellulosic materials (corn straw, wheat straw, and sawdust) are designed and installed in aquaponic systems. The BAFs performed the fish sludge separation and nutrient conversion in a single equipment without the necessity for backwashing. The potential for nutrient recovery from fish sludge is evaluated by comparing four BAFs filled with different media. The BAF with ceramsite plus sawdust achieves the highest mineralization capacity based on nitrification and dissolved total phosphorus. The average concentrations of N, P, K, Ca, Mg, and S macronutrients reach 12.3%, 11.8%, 4.5%, 26.4%, 22.6%, and 46.0% of those of Hoagland nutrient solution, respectively. The recovered Fe, Mn, and B micronutrients are 10.0%, 12.0%, and 18.0%, respectively, whereas Cu, Zn, and Mo are 1.5, 1.8, and 1.0 times, respectively, of those of Hoagland nutrient solution. The estimated nutrient recoveries of Ca, Mg, and S have good performance efficiencies, followed by K and Cu; those of N, P, Fe, Mn, and Zn have potentials for further improvement. The modified aquaponics with BAFs are proposed for the recovery of both dissolved and solid nutrients.

Small- and large-scale biochar-based filtrations were conducted to investigate the potential of biochar as a low-cost renewable filtration medium in aquaponics. The small-scale experimental design investigated the effects of 2 biochar media sizes (1 – 3 mm [referred to as fine biochar] and 3 – 5 mm [referred to as coarse biochar]), 3 biochar bed heights (2.5, 5.0 and 10.0 cm) and 3 loading rates (5, 10 and 15 m3/m2/d) on particle size distribution as well as turbidity removal efficiency. Both biochar sizes (fine and coarse) were able to clarify fish effluent. However, fine biochar led to better filtration characteristics compared to coarse biochar. Results indicated that biochar filter bed heights and loading rates affected the filtration performances. Using deeper filters combined with lower loading rates led to greater removal of suspended particles and turbidity compared to shallower filters and/or higher loading rates. Results from the large-scale filtration, using a mixture of fine and coarse biochar media (size of 1 – 5 mm), revealed that the ideal loading rate for maximizing the removal of turbidity from fish effluent in high-intensity aquaponic system for production of Nile tilapia and greenhouse plants (with 80 m3 total volume of water, 40 kg/m3 average stocking density and 15 kg/d feeding rate) was 10 m3/m2/d. This study suggests that biochar-based filtration could be incorporated into aquaponics as a polishing step before sending the water to plant growth systems.

The production of vegetables in aquaponic systems has high sustainability and conservation of natural resources, but studies that make their cultivation feasible under Brazilian conditions are still incipient. Given the influence that the cultivation system can cause on the postharvest characteristics of fruits and vegetables, this study aimed to evaluate the postharvest quality of yellow pear tomato cultivated in an aquaponic system. Tomato plants were grown in a protected environment, in the experimental area of aquaponics of the Faculty of Agrarian Sciences, belonging to the Federal University of Grande Dourados. The experimental design was completely randomized in a factorial scheme, with two factors: maturity stage at harvest and storage time. Three stages of fruit maturity (green, intermediate and ripe) and two storage times (zero and 35 days) were analyzed. Tomato samples were subjected to the analyses using the whole fruit, evaluated for mass loss, color and firmness, and the fruit pulp, evaluated for soluble solids (SS), titratable acidity (TA), SS/TA ratio, pH and lycopene content. The fruits of yellow pear tomato cultivated in aquaponic system were in satisfactory conditions with respect to the postharvest parameters evaluated, indicating great potential to be cultivated on a commercial scale under Brazilian conditions. The parameters analyzed were similar or superior to the parameters of tomatoes grown in other cropping systems.

Aquaponics as a potential alternative for conventional aquaculture industry has increasingly attracted worldwide attention in recent years. However, the sustainable application of aquaponics is facing a growing challenge. In particular, there is a pressing need to better understand and control the accumulation of dissolved organic matter (DOM) in aquaponics with the aim of optimizing nitrogen utilization efficiency. This study was aiming for assessing the characteristics of DOM in the culture water and the relationship with the nitrogen transformations in different intensified aquaponic systems with hydroponic aeration supplement and polylactic acid (PLA) addition. Two enhancing attempts altered the quantity of DOM in aquaponic systems significantly with a varying DOM content of 21.98–45.65 mg/L. The DOM could be represented by four identified fluorescence components including three humic -like materials (83–86%) and one tryptophan-like substance (14–17%). The fluorescence intensities of humic acid-like components were decreased significantly after the application of intensifying strategies, which indicating that two enhancing attempts possibly affected humic acid-like fluorescence. Variation of optical indices also suggested the reductions of water DOM which could be impacted by the enhancing nitrogen treatment processes. These findings will benefit the potential applications and sustainable operation of these strategies in aquaponics.

A simple and innovative concept for a micro-aquaponic system (MAS) to valorize residual nitrogen via photocatalytic conversion was developed. Results proved that over 70% of ammonia could be oxidized to nitrates within 1.5 hours under UV irradiation and subsequently taken up by plants which experienced a remarkably superior plant growth (with results showing 1.8–1.6 times improved petiole growth) with respect to standard grown samples. The proposed methodology may pave the way to a new eco-farming paradigm aimed at maximizing the value of residues to valuable end-products by combining multidisciplinary efforts and low environmental impact technologies.