Optimal Water Quality Research Articles

The effects of indigenous microorganisms and water treatment with ion exchange resin on Cu-Ni flotation performance

Mineral processing utilizes large amounts of water and aims to reduce water consumption by recirculation and closing the water loops. This results in accumulation of chemical and biological contaminants in process water that may have adverse outcomes on the process performance. To optimize water quality suitable for each process step and plant, knowledge of both chemical and biological effects are needed as well as techniques to best remove the contaminants. This study focused on the consequences of microorganisms, enriched from the actual process earlier, on the flotation performance in the multi-metal Kevitsa mine in Northern Finland and the applicability of ion exchange for the removal of dissolved sulfur species and microorganisms from water. The increase of microbial load from the original 106 to added 107 16S rRNA copies mL−1 affected positively the flotation selectivity, especially in the case of nickel. Two tested water types, process water (PW) and final tailings water (FT), behaved slightly differently. In the Cu flotation phase added microorganisms did not affect the Cu recovery of FT but decreased significantly the recovery of Cu in PW. With equal Cu grade, the recovery was as high as approximately 25 percentage points lower. However, added microorganisms in both water types decreased notably the recovery of Ni in Cu concentrate (18 to 37 %-points). At the same time the amount of Ni recovered in the Ni concentrate increased by 18 to 33 %-points with added microorganisms. Visually the froth layer was higher and more stable in the Ni flotation in experiments with added microorganisms compared to experiments without added microorganisms. The concentrations of dissolved sulfate and thiosulfate ions were low in the studied waters compared to operations treating massive sulfide ores and did not significantly affect the flotation performance. For this reason, the IX water treatment was not required for these ions. However, the IX treatment proved to be effective in removing both sulfur species and microorganisms. The use of dissolved air flotation (DAF) was a successful pretreatment for ion exchange in removal of microorganisms. However, microorganisms are not usually taken into consideration when process performance or water cleaning techniques are designed and optimization could result generally in even better outcome.

Bacteria-Mediated Synthesis of Iron Oxide Nanoparticles and Their Efficiency in Ammonia Removal from Fish Culture Tanks

Background: Aquaculture is one of the most rapidly expanding food production sectors. Due to intensification, declining water quality parameters negatively impact fish production and the surrounding environment. Thus, it is essential to maintain optimum water quality parameters and aquatic ecosystems for sustainable fish production. This study aims to synthesize nanoparticles (NPs) and evaluate their efficiency against ammonia in cultured fish tanks under diverse conditions. Methods: Bacillus megaterium from the soil sample was isolated and identified. Iron oxide NPs were synthesized using Bacillus megaterium collected from soil samples and characterized by DLS-zeta potential, UV-vis, XRD, FTIR, and TEM analysis. Next, synthesized NPs were evaluated under ex-situ and in-situ conditions to determine their efficacy in removing ammonia from Common carp, Cyprinus carpio culture tanks. Results: B. megaterium was isolated, identified, and 16S rRNA gene PCR-amplified sequences confirm the identification of B megaterium. DLS-zeta potential, UV-vis, XRD, FTIR, and TEM analysis revealed the quality of synthesized NPs. B. megaterium from the soil sample was isolated and identified. The mean zeta potential of the biosynthesized NPs was between -4.65 to -6.45 mV and had an average size of 5 nm. The concentration of ammonia in aerated tanks treated with iron NPs reduced to less than 0.03 mg/dL from 0.3 mg/L. Also, fish mortality in these tanks was significantly controlled with the application of NPs. The application of NPs considerably reduced fish mortality in these fish tanks. Iron oxide NPs from B. megaterium can produce high-quality NPs that are efficient in removing ammonia from fish culture tanks. Further, exploratory studies are necessary to determine the efficacy of iron oxide NPs on aquatic organisms cultured in different environments.

Evaluation of pollutant removal efficiency of urban stormwater wet ponds and the application of machine learning algorithms

Wet ponds have been extensively used for controlling stormwater pollutants, such as sediment and nutrients, in urban watersheds. The removal of pollutants relies on a combination of physical, chemical, and biological processes. It is crucial to assess the performance of wet ponds in terms of removal efficiency and develop an effective modeling scheme for removal efficiency prediction to optimize water quality management. To achieve this, a two-year field program was conducted at two wet ponds in Calgary, Alberta, Canada to evaluate the wet ponds' performance. Additionally, machine learning (ML) algorithms have been shown to provide promising predictions in datasets with intricate interactions between variables. In this study, the generalized linear model (GLM), partial least squares (PLS) regression, support vector machine (SVM), random forest (RF), and K-nearest neighbors (KNN) were applied to predict the outflow concentrations of three key pollutants: total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). Generally, the concentrations of inflow pollutants in the two study ponds are highly variable, and a wide range of removal efficiencies are observed. The results indicate that the concentrations of TSS, TN, and TP decrease significantly from the inlet to outlet of the ponds. Meanwhile, inflow concentration, rainfall characteristics, and wind are important indicators of pond removal efficiency. In addition, ML algorithms can be an effective approach for predicting outflow water quality: PLS, GLM, and SVM have shown strong potential to capture the dynamic interactions in wet ponds and predict the outflow concentration. This study highlights the complexity of pollutant removal dynamics in wet ponds and demonstrates the potential of data-driven outflow water quality prediction.

Developed and Intelligent Structure of a Control for PV Water Treatment System

The subject of this work is a UV-irradiated water disinfection prototype intended for use in rural areas where access to water is difficult. Given the favorable climatic conditions of our country, the use of photovoltaic panels as a source of energy is particularly interesting, and has relevance in regions with a similar climate. PV energy being a fluctuating source that influences water disinfection operations, we have developed a database to distribute the energy available to the loads (UV lamps, electric pumps) in order to ensure a better quality of the water. This database is used in deep learning to model water disinfection phenomena. This method is able to adjust the speed instructions of the motor pump (therefore the flow rate) and the UV irradiation according to the energy available to ensure optimal water quality. Several other techniques have been implemented to control the instructions generated by the deep learning developed, to control the motor, the inverter and the DC/DC converter (IRFOC, SVPWM, sliding mode). All these approaches are tested in real time and they represent good results in terms of water treatment control. The effectiveness of these types of control is proven by the results obtained.

Design and Development of User-Friendly Vertical Aquaponics Set-up for Ornamental Fish and Plants

One vertical aquaponics unit following the principle of Nutrient Film Technique (NFT) has been designed and developed at ICAR-Central Institute of Freshwater Aquaculture, Bhubaneswar centre of All India Coordinated Research Project on Plasticulture Engineering in Agriculture Structures and Environment Management (AICRP on PEASEM). The developed unit is constructed using three major components, viz., fish tank/ aquarium tank (0.127 m3), vertical hydroponic pipe (Ø0.16×1.5 m) and the water distribution system. The unit experimented with 30 numbers of Guppy fish (Poecilia reticulata) in 0.1 cubic meters of water and 6 numbers of Petunia plant (Petunia × hybrida) and 6 numbers of Zinnia plant (Zinnia angustifolia) in 780 CC hydroponics cups arranged at 20° from the vertical axis on a PVC pipe. The quad channel sprinkler is fixed inside the pipe at the top surface. The water dispersion efficiency concerning the availability of nutrient-rich water at the roots of the plants for its flowering has been evaluated in the present study. The optimum water quality and flower production from the plants were achieved at 200 LPH flow rate from the fish tank. At this hydrolic loading rate, maximum plant length & spread were observed among the three replications . The length & spread for Zinnia angustifolia and Petunia x hybrida were 37.17±4.27 cm & 39.54±7.45 cm, and 33.43±2.53 cm & 29.58±7.26 cm respectively. There was no significant difference (p>0.05) in the water quality parameters at 200 & 250 LPH flow rates in the vertical aquaponics system.The cost of one unit is calculated to be INR 7000, with approximately a 10-20% price reduction in case of mass production. The newly developed integrated system of aquarium is designed for peri-urban and urban hobby farming as well as home decoration.

Adding Sustainability in Analytical Chemistry Education through Monitoring Aquarium Water Quality

This paper introduces a captivating topic for upper-level analytical chemistry capstone projects, focusing on aquarium water analysis. This provides a more comprehensive understanding of the role of analytical chemistry towards sustainability and its environmental, economic, societal and education dimensions. Regarding the crucial role of maintaining optimal aquarium water quality for the welfare of aquatic life, students are tasked with envisioning and executing the measurement of key parameters, including pH, ammonium, nitrite, and nitrate contents. This hands-on experience not only engages students in real-world applications, but also allows them to delve into essential analytical chemistry principles. They carefully select measurement methods, considering factors such as instrument availability, ease of use, precision and sensitivity requirements, sample size, and matrix effects. Besides fostering the acquisition of technical and soft skills, one notable aspect of this type of project is the exceptionally high student satisfaction. Furthermore, the project’s outcomes have proven to be significant predictors of learning achievements. Additionally, it lays the foundation for exploring potential designs of aquaponics systems and fosters interdisciplinary projects, expanding the practical applications in the field of chemistry education. Overall, these projects exemplify enriching and engaging educational experiences that empower students with valuable skills and knowledge while encouraging them to explore novel avenues in analytical chemistry.

Application aquaponics biofloc of sangkuriang catfish (Clarias sp.)

The value of catfish production in Indonesia has decreased drastically every year. Increasing stocking density can be a solution to increase production, but it will have a negative impact on decreasing water quality which will also disrupt catfish production. Therefore, it needs to be accompanied by the application of biofloc and aquaponics technology which plays a role in maintaining optimal water quality while providing additional natural feed (floc) which can reduce feed use and reduce water usage. This study aims to increase the production value of sangkuriang catfish through the application of biofloc and aquaponic systems. This research was conducted in October-November 2022 at the Raudhatul Ulum Sakatiga Agribusiness Group, Ogan Ilir Regency. This study was designed using a comparison experiment. The treatments given consisted of P0 (control), P1 (Maintenance of sangkuriang catfish aquaponic biofloc of kale plant), and P2 (Maintenance of Sangkuriang catfish aquaponic biofloc of lettuce plant). The results showed that P2 was the best treatment which resulted in absolute growth in weight and length of 7.18 g and 3.74 cm, survival of 98%, and growth in length of kale of 30.9 cm.Keywords: aquaponics; biofloc; sangkuriang catfish

Water Quality Monitoring and Alert System for Fish Farms using IoT and SMS Integration

Abstract-This project proposes a water quality monitoring and alert system for fish farms using IoT (Internet of Things) and SMS (Short Message Service) integration. The system aims to ensure optimal conditions for fish growth and health by continuously monitoring important water parameters. IoT devices equipped with water quality sensors are deployed throughout the fish farm to collect real-time data on temperature, pH level, humidity and water level. The collected data is transmitted to a cloud-based platform via an IoT network for processing and analysis. If any parameter exceeds the acceptable limits, the system triggers SMS alerts to fish farm operators, providing timely notifications of potential water quality issues. Additionally, the system offers SMS-based remote control capabilities to enable immediate corrective actions. By combining IoT and SMS technologies, this system enhances the efficiency and effectiveness of fish farm management, enabling proactive responses to maintain optimal water quality and promote healthy fish growth. Keywords—aquaculture; wireless transmission; life expectancy; Internet of Things; robotic arm

Designing a Water Temperature control and Monitoring System for Vaname Shrimp cultivation based on the Internet of Things ( IoT )

Vannamei shrimp cultivation (Litopenaeus Vannamei) is one of the rapidly growing industries in fisheries. Optimal water quality, including the appropriate water temperature, is a crucial factor in maintaining the growth and health of vannamei shrimp. Therefore, this research aims to design and implement a monitoring and water temperature control system using a microcontroller in vannamei shrimp cultivation. The research method involves the development of a system prototype consisting of water temperature sensors, microcontrollers, and temperature control modules. The water temperature sensor is used to measure the water temperature in the vannamei shrimp cultivation pond, while the microcontrollers are responsible for acquiring temperature data from the sensor and controlling the temperature control modules based on predetermined parameters. The research results show that the monitoring and water temperature control system using microcontrollers can accurately measure the water temperature with high precision. The obtained temperature data can be displayed in real-time through the microcontroller's screen or accessed via computer-based applications. Moreover, the system is also capable of adjusting the temperature according to the setpoint, utilizing LEDs lights (red, green, yellow) US indicators for activating and deactivating the heating and cooling device. in field trials, this system was implemented in vannamei shrimp cultivation ponds of a specific size.

Automation System for Optimum Water Quality Maintenance in Tropical Fish Culture

Automation System for Optimum Water Quality Maintenance in Tropical Fish Culture

The Importance Of Seaweed As Bioremediation Natural Agent

Seaweed has emerged as a promising bioremediation agent for addressing heavy metal contamination in aquatic environments. This study presents a comprehensive review of ten selected references to explore the potential of seaweed-based bioremediation and its implications for environmental sustainability. The findings highlight the significant capacity of seaweed species to accumulate heavy metals, emphasizing the importance of species selection based on their metal uptake capabilities. Seaweed biomass and biochar demonstrate remarkable adsorption properties, providing efficient means of removing heavy metals from contaminated water through physical adsorption and ion exchange processes. Seaweed-based bioremediation techniques offer several advantages over traditional methods. The studies underscore the importance of considering environmental conditions and the presence of coexisting pollutants in designing seaweed-based bioremediation strategies. Optimal light availability, temperature, nutrient levels, and water quality parameters are critical for maximizing seaweed's metal removal efficiency. Overall, seaweed-based bioremediation offers a promising and sustainable approach for addressing heavy metal pollution in aquatic environments. Future research should focus on overcoming challenges related to biomass management, ecological impacts, and scaling up cultivation and processing methods to ensure the widespread implementation of this eco-friendly solution.

Stability of arsenic(Ⅲ, Ⅴ) in galvanized steel pipe scales coexisting with colloidal polystyrene microplastics under drinking water conditions

The stability of metalloid arsenic (As(Ⅲ)) and As(V) in corrosion scales of drinking water distribution systems (DWDS) is closely related to drinking water safety. The effects of colloidal microplastics entering the DWDS on the stability of As(Ⅲ) and As(V) have not been understood. This study investigated the migration and transformation behaviors of As (Ⅲ) and As(V) in the galvanized steel pipe scales employing speciation simulation and sequential extraction methods. The stability of As(Ⅲ) and As(V) in the pipe scales coexisting with colloidal polystyrene microplastics (CPMPs) under drinking water conditions was studied for the first time from the release behaviors and form distributions. Finally, the optimum water quality conditions for As(Ⅲ) and As(V) fixation were summarized. The existing forms of As(Ⅲ) and As(V) under different pH conditions, the competitive action of anions, and the hydrolysis of cations all would significantly affect the stability of As(Ⅲ) and As(V). Sequential extraction method results revealed that the content of As fractions increased in different forms after the pipe scales adsorbed As(Ⅲ) and As(V). The contents of As and iron (Fe) in the form of residual fractions increased in the presence of CPMPs. The effect of three cations on the stability of As(Ⅲ) and As(V) was Fe3+ > Zn2+ > Ca2+. Neutral to weak alkalescence, proper Cl− and cation concentrations were conducive to the fixation of As in DWDS. Notably, the presence of CPMPs could increase the stability of As(Ⅲ) and As(V) in corrosion scales, thus reducing the risk of metalloid As release in DWDS.

Climate smart carp hatchery: Bringing resilience to sustainable fish seed production

Since climate change is disproportionately affecting the aquaculture sector, the conversion of Eco-carp hatcheries to climate smart carp hatchery will be a remarkable adaptation by developing countries that can aid the farmers to cope with the climate change scenario. The alterations in the monsoonal rain patterns due to climate change poses a major threat to the quantity and quality of aquaculture production by directly affecting the water availability for fish farming in the near future. There are 2198 eco-carp hatcheries and 417 fiberglass reinforced plastics (FRP) carp hatcheries are operating in India. Due to the lack of technical knowledge to hatchery managers/owners, these hatcheries are following the conventional techniques that are incapable of withstanding the climate change impact. A climate smart carp hatchery with more control over key water parameters (DO, pH and temperature), through important modifications like a cooling tower/chiller, sensor-based monitoring and slow sand filter for recirculation of water have the potential to sustain the aquaculture sector by ensuring continuous production and supply of quality carp seed irrespective of the climate change risk. The present article cites the limitations of eco-carp hatchery to meet the optimum water quality parameters for carp breeding under climate change scenarios and suggests the transformation of eco-carp hatchery to climate smart carp hatchery.

Automated water quality monitoring and regression-based forecasting system for aquaculture

Water quality in fish tanks is essential to reduce fish mortality. Many factors affect the water quality, such as pH, dissolved oxygen, and temperature in fish tanks. Existing work has presented water quality monitoring systems for aquaculture, which are useful for automatic monitoring and notify any incidence of decline in water quality. It enables the fish farms to make interventions to reduce fish mortality. However, advanced monitoring through forecasting is necessary to ensure consistent optimum water quality. This paper presents a web-based water quality monitoring and forecasting system for aquaculture. First, a water quality forecasting model based on the long short-term memory is designed and developed. The model is evaluated and fine-tuned using the existing public dataset. Second, the prototype of the water quality monitoring and forecasting system is developed. An Arduino and Raspberry Pi based water quality data acquisition tool is built. A web-based application is then developed to present the monitoring data and forecasting. A notification module is included to send an alert message to the fish farmers when necessary. The system is tested and evaluated at the fish hatchery in Universiti Malaysia Sabah. The findings show that the proposed system provides better water quality management for fish farms.

Culture technique of seabass, Lates calcarifer in Asia: A review

Mariculture could be a new horizon in Bangladesh, and seabass is one of the most promising species. This paper goes into detail about seabass culture techniques and their future potential. Two culture methods have been prominent: Nursery to grow out culture and cage culture in coastal water. The study's main finding is that cannibalism occurs, resulting in mortality and failure to reach predicted growth. For seabass culture, the suitability of the site, whether for a pond or cage, is critical. The culture relies heavily on optimal water quality, particularly salinity maintenance. Proper feeding and disease management are also critical for higher production from the culture. One of the key concerns in seabass culture is the availability of live feed. Sea bass cage culture is extensively established in Malaysia, Indonesia, Thailand, Hong Kong, and Singapore. It could be a good option for culturing seabass in the coastal environment of Bangladesh although proper monitoring should be conducted. Seabass culture both in ponds or cages may contribute to our mariculture development and boost our national economy. This review will help the researchers, policymakers, entrepreneurs, and commercial culturists to introduce seabass for mariculture in the coastal regions which are salinity prone

Water quality assessment and pollution source apportionment using multivariate statistical and PMF receptor modeling techniques in a sub-watershed of the upper Yangtze River, Southwest China.

Rapid industrial and agricultural development as well as urbanization affect the water environment significantly, especially in sub-watersheds where the contaminants/constituents present in the pollution sources are complex, and the flow is unstable. Water quality assessment and quantitative identification of pollution sources are the primary prerequisites for improving water management and quality. In this work, 168 water samples were collected from seven stations throughout 2018-2019 along the Laixi River, a vital pollution control unit in the upper reaches of the Yangtze River. Multivariate statistics and positive matrix factorization (PMF) receptor modeling techniques were used to evaluate the characteristics of the river-water quality and reveal the pollution sources. Principal component analysis was employed to screen the crucial parameters and establish an optimized water quality assessment procedure to reduce the analysis cost and improve the assessment efficiency. Cluster analysis further illustrates the spatiotemporal distribution characteristics of river-water quality. Results indicated that high-pollution areas are concentrated in the tributaries, and the high-pollution periods are the spring and winter, which verifies the reliability of the evaluation system. The PMF model identified five and six potential pollution sources in the cold and warm seasons, respectively. Among them, pollution from agricultural activities and domestic wastewater shows the highest contributions (33.2% and 30.3%, respectively) during the cold and warm seasons, respectively. The study can provide theoretical support for pollutant control and water quality improvement in the sub-watershed, avoiding the ecological and health risks caused by the deterioration of water quality.

Designing and Implementing IoT-Based Water Quality Monitoring and Control System of a Pilot Scale Deep Flow Technique Aquaponics for Enhanced Crop-Fish Production

Aquaponics is an agricultural model that combines aquaculture and hydroponic cultivation systems, which can be a solution for expanding agricultural land in urban areas. The success of an aquaponics system heavily relies on maintaining optimal pond water quality, which serves as a vital source of nutrition for plants and ensures the survival of fish. Many studies have been conducted to build a system that maintains the good quality of pond water, but much of it only utilizes a limited number of parameters. This study was conducted to develop a robust control system capable of monitoring and regulating the water quality parameters, temperature, pH, dissolved oxygen (DO), and total dissolved solids (TDS), in real-time using IoT based system and fuzzy logic as a control method for decision-making. Users can monitor the condition of the pond using web interfaces that can be accessed via desktop or mobile devices. The design implementation results on the DFT aquaponics system showed an increase in the growth of paddy crops and tilapia with precision data recorded on the cloud server of 94.11%.

Streptococcosis in Sea Bream Sparus auratus with Special Reference to its Control by A Medicinal Plant

Isolation and identification of S. agalactiae from cultured sea bream by different microbiological methods, mortality rate, clinical signs, and postmortem lesions in sea bream in naturally and experimentally inoculated with a field sample of S. agalactiae. The aquarium trial was carried out with sea bream (Sparus auratus) in private fish farm at Borg El-Arab, Alexandria governorate Egypt. At total 50 of sea bream (Sparus auratus) was used during the study. The study lasted 10 weeks, starting with 50 ± 5 gram /fish. Prior to the start of the trial, the fish were fed with a commercial diet (45 percent CP, crude protein). Water quality parameters were monitored during fish acclimatization and throughout the trial. Water temperature, pH and dissolved oxygen remained within acceptable ranges for marine production during the trial. Our results concluded that, Streptococcus spp. (specifically S. agalactiae) is very pathogenic as they can affect sea bream which become a perfect host for Streptococcus infection. In addition, water quality parameter plays an important role in sea bream farming. In more specific, an optimum water quality parameter should be maintained to prevent “stress’’ in fish that can lead to outbreaks of disease. It can be concluded that the medicinal plant can help in prevention and control of bacterial infection in cultured fish, and because of their high resistance, to most antibiotics utilization in the prophylaxis or treatment of S. agalactiae infection should be avoided. The farmers must be used such approach to applied in the protocol of prevention of such infection in stead of chemotherapy.

Effect of Different Doses of Pituitary Gland (PG) Hormone on Induced Breeding of Bheda/Meni (Nandus nandus) Fish

An experiment on induced breeding of Bheda/Meni fish (Nandus nandus) was carried out to determine the optimum dose of pituitary gland hormone during December 2018 to June 2019 at Floodplain Sub-station of Bangladesh Fisheries Research Institute (BFRI), Santahar, Bogura. In this experiment, PG was used as inducing agent for both male and female fish. For induced breeding, PG was administered at the rate of 1, 2 and 3 mg/kg body weight to male brood fish, and correspondingly 2, 4 and 6 mg/kg body weight to female brood fish that were considered as the treatments namely, T1, T2 and T3, respectively. Fifty pairs of male and female fish were collected from the Raktadaha beel from where forty-five pairs were selected for induced breeding and the average body weight of the male and female were 43.0±2.5 gm and 55.2±3.0 gm in T1, 45.1±2.9 gm and 56.0±2.8 gm in T2, and 40.3±2.4 gm and 52.6±3.2 gm in T3. The male-female ratio was maintained as 1:1 in the breeding hapa. It was observed that female and male brood fishes ejected eggs and milt, respectively at the contemporary times. Ovulation occurs naturally after 8-10 hours of injection. The fecundity of fish (body weight 45 to 60 gram each) varied from 7,232-27,546. The fertilized eggs were hatched within 16-20 hours. The hatchlings were reared in rearing tank up to 5 days. The fertilization rate of Nandus nandus were 76±4 %, 93±5 % and 57±3 %, in T1, T2, and T3, respectively and the hatching rate were 72±3 %, 86±2 % and 61±4 % in T1,T2 and T3, respectively. Both the fertilization and hatching rates were significantly higher (p<0.05) in T2 treatment than T1 treatment followed by T3 treatment. The mean values of water temperature (°C) were 29.5±1.15, 30.0±2.03 and 30.8±1.76°C, pH was 7.4 ±0.46, 7.8±0.53 and 7.3±0.49 and dissolved oxygen (mg/L) were 5.5±0.61, 5.3±0.24 and 5.8±0.56 in brooder tanks, breeding hapa and larval hapa, respectively during the experiment and did not vary (P>0.05) among them and were suitable for induced spawning of Nandus nandus. Based on the findings of the present experiment, it was revealed that T2 showed the best outcome in terms of fertilization rate (93±5%) and hatching rate (86±2%) among the three treatments under optimum water quality parameters where PG hormone were used at the rate of 2 and 4 mg/kg body weight for male and female fish, respectively. Therefore, the present findings could be used in induced breeding of N. nandus for the development of hatchery propagation. Further trials on rearing or culture of this endangered fish under different stocking densities or feedings might be conducted at on-station and on-farm levels in Bangladesh as well as elsewhere of this region to save the fish from extinction or for its conservation and rehabilitation.

Metagenomic insights into feasibility of agricultural wastes on optimizing water quality and natural bait by regulating microbial loop

Effective screening feed substitutes for improving water quality in aquaculture systems has become a trending research topic now. In this study, three typical organic agricultural wastes, including sugar cane bagasse (SC), coconut shell powder (CS), and corn cob powder (CC), were selected to evaluate their potential roles on the optimization of water quality and natural bait compared to aquafeeds. Fish feed resulted in the highest growth rate of fish but the worst water quality. Organic detritus addition markedly improved the water quality, especially soluble reactive phosphorus (SRP, decrease of 56–61%) and ammonium (decrease of 16% in SC, 47% in CC). Specially, SC induced core microbes to mediate nutrients transformation and recycling (N2-fixation, ammonification, nitrification, dissimilatory nitrate reduction to ammonia and organic nutrients decomposition), which facilitated the primary productivity based on their positive relationships. This further reduced the available nutrients (especially SRP) in the water and built a mutually beneficial microbial loop. In addition, SC addition increased the abundance of genes involved in amino acids biosynthesis pathways, photosynthesis, and carbon fixation. These results led to energy transfer to higher trophic levels. The addition of CC had a better effect than SC in terms of lower nitrogen levels and a higher fish growth rate (19% in CC, 5% in SC). However, low temperatures and carbon accumulation jointly drive the anaerobic decomposition, resulting in unhealthy microbial loops and low fish growth rates. In contrast to the direct consumption of fish feed, organic detritus can induce more natural bait to provide food for fish by regulating the microbial loop, as showed by the microbial community composition in the water and fish gut. To comprehensively assess water quality, natural bait, and fish growth and quality, certain organic detritus should be considered as an auxiliary material to partially replace feed for healthy and sustainable aquaculture systems.