Insect shell chitosan nanoparticle as novel flocculants in biofloc system: An innovative resource recovery approach for sustainable aquaculture

Tilapia (Oreochromis niloticus) is one of the most important species in aquaculture, so the optimization of its culture by using sustainable strategies is fundamental. The aim of this study was to evaluate the effects of incorporating natural pigments (carrot and beetroot meal) as carbon sources in a biofloc system on the growth, immune response, and oxidative stress of O. niloticus. The experiment comprised four treatments: clear water as control (CT), biofloc with molasses (TBM), biofloc with carrot meal (TBC), and biofloc with beetroot meal (TBB). Results showed that biofloc helped to maintain optimal water quality and high survival rates, but specifically, TBC treatment achieved the highest growth rates and feed conversion ratio, along with elevated leukocyte counts, indicating improved health and immunity. Gene expression analysis revealed enhanced antioxidant activity (sod, gpx) and modulated immune responses (tnf-α, il-1β), particularly under thermal stress. Carrot meal emerged as an effective carbon source in biofloc systems, promoting growth, immune resilience, and oxidative stress resistance in tilapia, while beetroot meal improved pigmentation. These findings highlight the potential of natural pigments to enhance aquaculture sustainability and productivity.

Objective We investigated the effect of feeding frequency (FF-2 [2 times/d], FF-3 [3 times/d], FF-4 [4 times/d], and FF-5 [5 times/d]) on nursery-based co-culture of Pacific white shrimp Litopenaeus vannamei and giant river prawns Macrobrachium rosenbergii in a biofloc system. Methods The growth parameters, proximate composition, and hemocyte status of L. vannamei and M. rosenbergii were calculated. The physicochemical parameters, total bacterial load, and proximate composition of the biofloc were also measured among the treatments. Molasses was added (C:N ratio = 10:1), and salinity was 15‰. The experiment utilized twelve 125-L tanks, each containing 100 L of water. Each tank was stocked with 100 postlarvae, comprising 50 L. vannamei (mean ± SD = 28.38 ± 0.54 mg) and 50 M. rosenbergii (25.62 ± 0.31 mg). Results For L. vannamei, the specific growth rate (%/d) was significantly higher in FF-5 (mean ± SD = 9.87 ± 0.54) and lower in FF-2 (9.30 ± 0.46). For M. rosenbergii, the specific growth rate was significantly higher in FF-3 (5.78 ± 0.46) and lower in FF-2 (5.61 ± 0.46). The survival rate for L. vannamei was significantly higher in FF-5 (mean ± SD = 91.33 ± 6.43%) and lower in FF-2 (86.00 ± 13.86%). For M. rosenbergii, the survival rate was significantly higher in FF-5 (86.00 ± 7.21%) and lower in FF-2 (72.00 ± 10.58%). The feed conversion ratio was significantly better in FF-5 (1.29) for L. vannamei, whereas it was significantly better in FF-3 (2.08) for M. rosenbergii. Significantly higher hemocyte counts were recorded in FF-5 for both species. For L. vannamei and M. rosenbergii, significantly higher levels of crude protein, lipid, and ash were recorded in FF-5. The benefit–cost ratio was higher for FF-5 than for FF-4, FF-3, or FF-2. Conclusions This study indicates that higher feeding frequencies improved the survival rate of L. vannamei and M. rosenbergii and enhanced their economic viability, productivity, and sustainability in aquaculture.

This study aimed to evaluate the potential of coffee parchment (CP), an underutilized agro-industrial by-product, as a functional feed additive for Nile tilapia (Oreochromis niloticus) reared in a biofloc system. Coffee parchment is rich in bioactive compounds and may offer sustainable benefits to aquaculture. To assess its effects, 300 fingerlings (average weight 18.60 ± 0.09 g) were randomly allocated to five groups and fed diets containing 0, 5, 10, 20, and 40 g kg−1 of CP for eight weeks. Growth performance, immune responses, the expression of growth-, immunity-, and antioxidant-related genes, and gut microbiota composition were examined. The results showed that CP supplementation significantly improved growth and immunological parameters, with the best overall effects observed in the CP5 group. CP5 led to significant upregulation of ghrelin, galanin, EF-1α, NPY-α, IL-1β, TNF-α, NFkB, MHC II-α, Hsp70, GPX, and Nrf2 genes. Microbiota analysis revealed 69 shared ASVs across treatments, with CP supplementation causing clear shifts in bacterial composition. CP5 reduced Proteobacteria abundance and microbial richness and evenness, suggesting selective modulation of gut communities. Polynomial regression analysis based on growth performance data estimated an optimal CP dosage range of 15.06–19.86 g kg−1. In conclusion, coffee parchment is a promising functional feed additive that enhances growth, immunity, gene expression, and gut microbiota modulation in Nile tilapia reared in biofloc systems. These findings support its application in sustainable aquaculture; however, further validation under commercial farming conditions is recommended.

Enhancing growth, immunity, and gene expression in Nile Tilapia (Oreochromis niloticus) through dietary supplementation with avocado (Persea americana) seed powder

Recent progress towards the application of biofloc technology for tilapia farming

Dietary corn silk enhances growth, immunity, and gene expression in Nile tilapia (Oreochromis niloticus) cultured in a biofloc system.

Especially in arid regions, developing tilapia culture with the ability to survive a wide range of salinities is crucial due to the limited availability of fresh water for aquaculture. The present study focused on evaluating the growth performance of Nile tilapia in a biofloc system under three salinity levels: 0 (BFT0), 4 (BFT4), and 8 g/L (BFT8). Fingerling fish were raised for 37 days in tanks with a water volume of 140 liters and a stocking density of one fish per liter. The results of the water quality parameters showed that dissolved oxygen and pH decreased with increasing salinity. Furthermore, the BFT8 group had the highest concentrations of settled solid (19.98 ml/L) and total suspended solid (428.37 mg/L), while the BFT8 group had the lowest TAN concentration (4.32 mg/L). The final weight and specific growth rate were significantly higher in the BFT8 and BFT4 groups compared to the BFT0 group. Survival rates were not significantly different across treatments, and all of them were higher than 97%. The protein and lipid content of Nile tilapia bodies and bioflocs decreased with increasing salinity, while the ash content increased. The highest body ash content in Nile tilapia (13.81% of dry weight) and bioflocs (31.78% dry weight) was found at 8 g/L salinity. Based on the present study, it is suggested that salinities of 4 and 8 g/L can improve water quality, growth performance, survival, and carcass composition of Nile tilapia fingerlings in the biofloc system. This finding suggests that brackish waters can be utilized for sustainable aquaculture for the rearing of Nile tilapia.

The biofloc system is one of the novel sustainable aquaculture systems, and adding carbonaceous organic matter is the basis of the system. This study aimed to evaluate the effects of different carbon sources on water quality, biofloc composition, and growth performance of Nile tilapia (Oreochromis niloticus). In this study, one control group (no carbon source addition) and four biofloc treatments with molasses (TM), starch (TS), barley flour (TB), and corn (TC) addition with three replications were considered. Altogether, 160 Nile tilapia with an average weight of 1.7 g were stocked in each of the 300-l tanks (160 l of water volume). The results of water quality indicated that the lowest levels of dissolved oxygen (5.43 mg/l) and pH (7.28) were observed in the TS treatment, which showed a significant difference (P < 0.05) compared to other treatments. There was a significant difference among various treatments in nitrogen compounds and the total density of heterotrophic bacteria. Biochemical quality of biofloc was affected by various carbon sources. The highest levels of protein (31.09%), lipid (3.89%), and ash (32.79%) were observed in TB, TC, and TM treatments, respectively. The largest biofloc size was obtained in TS treatment. The lowest survival rate and the highest level of weight gain of Nile tilapia were observed in control group. In conclusion, the present study showed that different sources of carbon in the biofloc system have different effects on water quality, biochemical composition, and biofloc size produced in cultivation tanks.

BackgroundThe biofloc system (BFS) provides a sustainable aquaculture system through its efficient in situ water quality maintenance by the microbial biomass, besides continuous availability of these protein-rich microbes as feed to enhance growth and immunity of the reared organism. This study explores the gill architecture, growth performance, digestive enzyme activity, intestinal microbial composition, and histology of three freshwater fish species, Puntius gonionotus, Pangasianodon hypophthalmus, and Heteropneustus fossilis reared in biofloc based polyculture system.ResultsThe three species in T2 showed significantly higher WG and SGR, followed by T1 and T3. The wet mount of gill architecture showed smaller inter-filament gaps in gill arches of silver barb followed by stinging catfish and stripped catfish, but showed no correlation with the weight gain. However, silver barb being an omnivore and filter-feeder, accumulated a more diverse microbial community, both in T1 and BFS (T2 and T3), while the bottom feeder H. fossilis exhibited unique gut bacterial adaptability. The presence of floc in T2 and T3 enhanced bacterial abundance in water and fish gut, but their microbial diversities significantly reduced compared to T1 receiving only feed. Next-generation sequencing revealed that the Pseudomonas dominated in gut of P. gonionotus and P. hypophthalmus in T1, Enterobacterales and Fusobacterium prevailed in those of T2 and T3, respectively. In contrast, gut of H. fossilis had the highest proportion of Clostridium in T1, while Rhizobiaceae dominated in T3. Similarly in floc samples, Enterococcus dominated in T1 while Micrococcales and Rhizobiaceae dominated in T2 and T3, respectively. A positive correlation of enterobacteria, with the digestive enzyme activities and growth patterns was observed in all treatments.ConclusionThe present study revealed feeding behaviour to play crucial role in distinguishing the gut microbial composition patterns in fishes reared in Biofloc System. Further it revealed the requirement of supplementary feed along with floc in these three species for higher growth in the biofloc system.

The 8-week study evaluated the effect of dietary protein reduction on growth performance and water quality of blue streak hap (Labidochromis caeruleus) using biofloc technology (BFT). Fish averaging 0.67 ± 0.13 g in weight were distributed into 15 polyester tanks, each with a water volume of 60 L within 100 L tanks, accommodating 15 fish per tank. Four isolipidic and isoenergetic diets were formulated with gradually decreasing protein levels (40%, 35%, 30%, and 25%). Four biofloc groups (40P + BF, 35P + BF, 30P + BF, and 25P + BF) and control (C) (40P + without BF) were fed twice daily (09:00 and 17:00) at a rate of 5% of their body weight. Molasses was added to the experimental tanks on a daily basis as an organic carbon source. This ensured that the biofloc tanks had a balanced carbon/nitrogen (C/N) ratio and facilitated control of total ammonia nitrogen (TAN), nitrite-nitrogen (NO2-N), and nitrate-nitrogen (NO3-N) levels. The nutritional composition of the bioflocs obtained from the experimental groups revealed that the crude protein and crude lipid contents were 37.00–38.14% and 1.45–1.52%, respectively (P > 0.05). The best specific growth rate (SGR) (1.68%) and feed conversation ratio (FCR) (2.21) were determined in the 35P group. Based on the overall evaluation of the study’s data, it can be concluded that the dietary protein for the blue streak hap (L. caeruleus) can be reduced from 40 to 35% in a biofloc system without any negative effects on health. Improving water quality and providing additional food to fish through zero water exchange and organic carbon addition (BFT) can be considered a sustainable aquaculture technique that can be used in ornamental fish farming.

Dietary chitosan supplementation in Litopenaeus vannamei reared in a biofloc system: Effect on antioxidant status facing saline stress

In face of the shortage of, and competition with, land and water, the sustainability of aquaculture will have to depend on vertical development, through improving production environments, increasing productivity and enhancing aquaculture technologies. Biofloc technology (BFT) has emerged as new alternative for sustainable aquaculture, which could contribute to FAO Sustainable Development Goals (SDGs) related to food security. Extensive research has been carried out on the development and application of BFT in aquaculture since early 1990s, with emphasis on shrimp culture. Over 40% of BFT publications in aquaculture were directed to shrimp farming. Therefore, I strongly believe that the accumulated knowledge on the applications of BFT in shrimp farming and the experience gained, especially during the last 10 years (2010–2020), are now more than worthy of critical review and analysis. This review summarizes the most update knowledge on the use of BFT in different marine shrimp and freshwater prawn aquaculture. Emphasis has been on factors affecting shrimp production in BFT systems, integration of biofloc‐based shrimp farming with other aquatic farmed species, nutritional value of bioflocs as a natural food or feed ingredient for farmed shrimp and prawn, the application of BFT in different rearing phases, the use of biofloc as a natural probiotics and their effects on shrimp health and physiological functions, economic considerations and commercial applications of BFT‐based shrimp aquaculture, and the major challenges facing shrimp farming in biofloc systems.

Biofloc technology aims to maximize fish farming productivity by effectively breaking down ammonia and nitrite, promoting healthy flocculation, and enhancing the growth and immunity of cultured animals. However, a major limitation in this field is the suitable starter microbial culture and narrow number of fish species that have been tested with the biofloc system. Here, we investigated various microbial inoculum containing beneficial microbes with probiotics, immunostimulatory and flocs development and bioremediation properties would lead to the development of ideal biofloc development. Three treatment groups with different microbial combinations, viz., group 1 [Bacillus subtilis (AN1) + Pseudomonas putida (PB3) + Saccharomyces cerevisiae (ATCC-2601)], group 2 [B. subtilis (AN2) + P. fluorescens (PC3) + S. cerevisiae (ATCC-2601)] and group 3 [B. subtilis (AN3) + P. aeruginosa (PA2) + S. cerevisiae (ATCC-2601)] were used and compared with the positive control (pond water without microbial inoculums) and negative control (clear water: without microbial inoculums and carbon sources) on biofloc development and its characteristic features to improve the water quality and growth of fish. We demonstrated that microbial inoculums, especially group 2, significantly improve the water quality and microbiota of flocs and gut of the test animal, Heteropneustes fossilis. The study further demonstrates that biofloc system supplemented with microbial inoculums positively regulates gut histomorphology and growth performance, as evidenced by improved villous morphology, amylase, protease and lipase activity, weight gain, FCR, T3, T4 and IGF1 levels. The inoculums induced an antioxidative response marked by significantly higher values of catalase (CAT) and superoxide dismutase (SOD) activity. Furthermore, the supplementation of microbial inoculums enhances both specific and non-specific immune responses and significantly elevated levels of immune genes (transferrin, interleukin-1β and C3), and IgM was recorded. This study provides a proof-of-concept approach for assessing microbial inoculums on fish species that can be further utilized to develop biofloc technology for use in sustainable aquaculture.

Biofloc technology (BFT) is a promising new approach that has the potential to balance the needs of increased fish food production and sustainable aquaculture. Of late, there has been growing research on BFT and several reviews have been published that highlight the benefits of this technology. Studies focused on topics, including nitrogen recycling, carbon source selection, probiotics, species selection, stocking, and biofloc-based coupled models. However, the scope of research on BFT is expanding, and it is important to examine the latest findings to identify the future course of action. A recent literature search identified the use of novel flocculating agents in the BFT. The use of novel flocculating agents (such as chitosan) is a new approach to improving water quality in BFT systems. These advances include the development of new flocculants and the development of new biofloc-based feeds and supplements. The benefits of good flocculants in the BFT are as follows, i) improved floc formation, ii) improved water quality and reduced sludge production, iii) removal of heavy metals, iiii) microplastic degradation, and iiiii) improved fish and shrimp growth performance. In this review, the importance of flocculating compounds in the biofloc system are discussed.

A 65-day comparative study was conducted to evaluate the effects of three culture systems Biofloc (T1), Bio phyton (T2), and Aquamimicry (T3) alongside a control (T4) on growth performance, water quality parameters, proximate composition, and microbial dynamics of Catla catla fingerlings (initial weight: 0.69 ± 0.02 g). Millet was used as a carbon source in all treatments, whereas no carbon source was added in the control. Among all treatments, Biofloc technology (T1) exhibited superior performance across most evaluated parameters. Fish reared under T1 showed significantly higher body weight gain (39.49 ± 4.35%), specific growth rate (2.30 ± 0.01), feed efficiency ratio (0.88 ± 0.07), protein efficiency ratio (2.20 ± 0.17), lipid efficiency ratio (14.67 ± 1.18), and survival rate (90.21 ± 1.77), along with a lower feed conversion ratio (1.15 ± 0.09), compared to other treatments. Water quality parameters in T1 remained within optimal ranges throughout the experimental period, reflecting efficient nutrient recycling and enhanced microbial activity. Microbial analysis through total plate count (TPC) revealed significantly higher microbial abundance in both water and fish gut samples under Biofloc (T1), followed by Bio phyton (T2), Aquamimicry (T3), and the control (T4). In water samples, T1 (3.5107CFU/ml) and T2(3.2107 CFU/ml) recorded the highest TPC values, while similar trends were observed in fish gut samples, with T1 exhibiting the maximum microbial load. The elevated microbial populations in biofloc systems likely contributed to improved nutrient assimilation, health status, and growth performance of fish by promoting beneficial heterotrophic microbial communities. the findings demonstrate that millet-based biofloc technology effectively enhances microbial abundance, water quality, and growth performance of C. catla, suggesting its suitability as a sustainable and productive aquaculture strategy.