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Biofloc technology is commonly applied in intensive tilapia (Oreochromis niloticus) culture to maintain water quality, supply the fish with extra protein, and improve fish growth. However, the effect of dietary supplementation of processed biofloc on the gut prokaryotic (bacteria and archaea) community composition of tilapia is not well understood. In this study one recirculating aquaculture system was used to test how biofloc, including in-situ biofloc, dietary supplementation of ex-situ live or dead biofloc, influence fish gut prokaryotic community composition and growth performance in comparison to a biofloc-free control treatment. A core gut prokaryotic community was identified among all treatments by analyzing the temporal variations in gut prokaryotes. In-situ produced biofloc significantly increased the prokaryotic diversity in the gut by reducing the relative abundance of dominant Cetobacterium and increasing the relative abundance of potentially beneficial bacteria. The in-situ biofloc delivered a unique prokaryotic community in fish gut, while dietary supplementation of tilapias with 5% and 10% processed biofloc (live or dead) only changed the relative abundance of minor prokaryotic taxa outside the gut core microbiota. The modulatory effect of in-situ biofloc on tilapia gut microbiota was associated with the distinct microbial community in the biofloc water and undisturbed biofloc. The growth-promoting effect on tilapia was only detected in the in-situ biofloc treatment, while dietary supplementation of processed biofloc had no effect on fish growth performance as compared to the control treatment.

Biofloc technology (BFT) has been identified as an effective and sustainable aquaculture method, particularly beneficial for warm-water species in tropical areas. This technology is widely used in intensive aquaculture for several aquatic species due to its capacity to significantly reduce water exchange rates, benefiting both production systems and the environment. The efficacy of BFT in farming operations is directly related to a proper management of water quality parameters within the optimal range of the target species, as these parameters directly impact the yield of production units. Essentially, BFT functions as a water quality management system, converting harmful nitrogenous waste such as ammonia and nitrite into less harmful forms such as nitrates through microbial activity, ensuring the health of aquatic organisms. Key environmental factors such as temperature, dissolved oxygen (DO), pH, salinity, alkalinity, TAN, nitrite, nitrate, settleable solids (SS), and total suspended solids (TSS) can affect the growth of aquatic species and the functionality of the microbial community. This review brings (i) a comprehensive bibliometric analysis on biofloc and water quality, (ii) highlights optimal ranges, and (iii) key observations of several water parameters including temperature, salinity, nitrogenous compounds, SS, TSS, DO, phosphate, pH, and alkalinity in BFT rearing conditions for key aquatic species. Elements such as countries, thematic and keywords, and authors were explored, correlated, and discussed. In addition, this manuscript also (iv) discusses the presence of heavy metals and microplastics (MPs) in BFT culture water. A dedicated review on water quality in biofloc technology will contribute to future research and development (R&D) in this topic, support decision-making to improve farming operations, and can help further expansion of BFT-based aquaculture.

Some aspects of traditional aquaculture have negative impacts on the aquatic environment, leading to pollution and disease outbreaks in farmed organisms. Biofloc technology (BFT) is a closed aquaculture system that utilizes specific microbial communities to remove ammonia emitted from aquaculture organisms or adds carbon to the aquaculture system to improve water quality. BFT has benefits, such as increasing production and improving water quality, and reducing disease spread and pollution, without the need for water exchange. However, there are disadvantages, such as rapid changes in water quality due to accumulation of dissolved nutrients and total suspended soils (TSS) and the requirement for expensive aeration equipment to maintain dissolved oxygen. BFT can be enhanced in value and efficiency by combining it with other aquaculture technologies, such as aquaponics and vertical aquaculture to overcome the disadvantages. The integration of biofloc with technologies from the fourth industrial revolution holds potential for further development, while aquaponics and vertical farming can eliminate geographical limitations and accelerate the urbanization of aquaculture. The integration of aquaponics and vertical aquaculture with BFT has potential for development, accelerating the urbanization of aquaculture and removing geographic limitations.

Single-cell ingredients (SCI) are a relatively broad class of materials that encompasses bacterial, fungal (yeast), microalgal-derived products or the combination of all three microbial groups into microbial bioflocs and aggregates. In this review we focus on those dried and processed single-cell organisms used as potential ingredients for aqua-feeds where the microorganisms are considered non-viable and are used primarily to provide protein, lipids or specific nutritional components. Among the SCI, there is a generalised dichotomy in terms of their use as either single-cell protein (SCP) resources or single-cell oil (SCO) resources, with SCO products being those oleaginous products containing 200 g/kg or more of lipids, whereas those products considered as SCP resources tend to contain more than 300 g/kg of protein (on a dry basis). Both SCP and SCO are now widely being used as protein/amino acid sources, omega-3 sources and sources of bioactive molecules in the diets of several species, with the current range of both these ingredient groups being considerable and growing. However, the different array of products becoming available in the market, how they are produced and processed has also resulted in different nutritional qualities in those products. In assessing this variation among the products and the application of the various types of SCI, we have taken the approach of evaluating their use against a set of standardised evaluation criteria based around key nutritional response parameters and how these criteria have been applied against salmonids, shrimp, tilapia and marine fish species.

Abstract Stocking density of fish is species specific and is considered as one of the crucial aspects for optimizing feed and water-quality management in biofloc system. The present study was carried out to determine the optimum stocking density of a prime aquaculture species, climbing perch Anabastestudineus in biofloc system. Fish fingerlings with a mean initial weight of 0.80 ± 0.02 g were reared in biofloc tanks for 13 weeks under three different stocking densities, 300 (T-300), 450 (T-450), and 600 (T-600) fish m−3 in triplicates, and the fish were fed with a commercial diet at 3% of their body weight. At final harvest, significant differences in growth and body composition were observed among the treatments. T-300 and T-450 showed similar growth pattern (p > 0.05), while fish in T-600 registered significantly poor growth (p < 0.05). The fitted models for all the growth variables were quadratic, and daily individual feed intake was linear. Although the regression model for yield was not significant (p = 0.072), the highest yield (kg m−3) was attained in T-450. Dry matter, protein, and lipid content of fish remained unaffected (p > 0.05), while significant (p < 0.05) difference in ash content was observed among the treatments with the highest being found in fish from T-600. These results suggest that at the initial stage of culture the optimum stocking density of climbing perch in biofloc system is 300–450 fish m−3 although higher stocking might be feasible considering periodic water exchange and solid management, a proposition awaits further elucidation.

The current study was conducted to evaluate the effects of increasing carbon to nitrogen (C/N) ratios on water quality, growth performance, and body composition of Litopenaeus vannamei juveniles. Shrimp with initial average weight of 2.50 ± 0.3 g were cultivated for 35 days in 300-L tanks (160 L of water volume) with a density of 1 g per liter. The experiment was performed in five treatments with three replicates. One control group and four biofloc treatments with different C/N ratio were considered: C/N of 10 (CN10), 14 (CN14), 18 (CN18), and 22 (CN22). Shrimp were fed three times a day, and molasses just was added as a carbon sources to the biofloc treatments after each feeding. According to the results, the lowest amount of dissolved oxygen (5.33 mg L−1) and pH (7.83) was observed in CN22 treatment, which showed a significant difference with other treatments (P < 0.05). The highest level of total ammonia nitrogen (1.05 mg L−1) and nitrite (mg L−1) were recorded in control group, while the highest total density of heterotrophic bacteria was obtained in CN22 treatment. Growth performance parameters were at the highest level in the CN14 treatment, so the highest amount of final weight (6.88 g), biomass, and survival rate (94.79%) were observed in this treatment. The biochemical composition (protein, lipid, and ash) of the shrimp body and produced biofloc were affected by different C/N ratios, so these parameters were increased by rising of C/N ratio. In general, this study showed that the growth performance and body composition of Pacific white shrimp juveniles and water quality were suitable for rearing in biofloc system with C/N ratio of 14 than other treatments.

Abstract The study was conducted to evaluate the efficacy of biofloc meal incorporated diets on growth performance and physiological responses in Penaeus vannamei. The feeding trial was conducted using two control diets and four experimental diets, having biofloc meal at various incorporation levels, namely control diet (commercial diet), BFT0 (biofloc meal control, biofloc meal at 0%) BFT10 (biofloc meal at 10%), BFT20 (biofloc meal at 20%), BFT30 (biofloc meal at 30%), and BFT40 (biofloc meal at 40%). Healthy post larvae of P. vannamei (0.03 ± 0.00 g) were stocked (50 shrimp per tank) in a glass tank and fed with the experimental diets at 10% of animal body weight, four times a day, for a duration of 60 days. Among the different treatments, significantly higher final body weight (1.30 ± 0.06 g), weight gain (1.27 ± 0.06 g), specific growth rate (6.21 ± 0.01%/day), and survival rate (62 ± 0.20%) were recorded in BFT30 diet. In contrast, shrimp reared using control diet exhibited lower specific growth rate (5.53 ± 0.02%/day) and survival (48 ± 0.14%) compared to other treatment groups. At the end of the experiment, serum protein (1.6 ± 0.02 g/dl), prophenoloxidase (16.35 ± 2.98 U/mg protein), and peroxidase (0.2 ± 0.03 U/ml) were found to be significantly higher in BFT30 diet-fed group. Similarly, the digestive enzyme activities of amylase (4.75 ± 0.87 U/mg protein) and lipase (118 ± 5.10 U/mg protein) of BFT30 reared shrimp were found to be significantly higher. In addition, the histological observation of the shrimp revealed the larger proportion of mature cells with intracellular digestion (B) and absorption (R) in BFT30 group. Overall, the study revealed that biofloc meal incorporation at 30% in shrimp diet would potentially improves the growth performance and physiological responses of shrimp.

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.

The present study investigated the effect of stocking density and dietary carbon sources on the water quality, oxidative status, and immune-related genes of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions (BFT). Eight groups were established at two levels of stocking densities (140 fish per m3: low stocking density, LSD) and (280 fish per m3: high stocking density, HSD) (5.15 ± 1.12 g) and kept in eight biofloc units containing water without carbon sources (control groups) or with glycerol, molasses, or starch. Red blood cells count, hemoglobin, and hematocrit values were reduced in fish stocked in control groups at LSD and HSD than biofloc groups. Control fish groups reared at both LSD and HSD have the highest significant (p < 0.05) white blood cells number than other fish groups. Meanwhile, fish groups that received glycerol, molasses, and starch maintained in both LSD and HSD presented a higher significant (p < 0.05) monocyte % than in the control group reared at both LSD and HSD. The fish group reared in biofloc conditions (BFT) using starch carbon source and reared at the HSD presented a significantly higher (p < 0.05) increase in total serum protein and albumin levels as well as globulin value than the control fish group reared at both LSD and HSD. The highest glucose and cortisol levels were showed in the control fish group reared at both LSD and HSD. Fish maintained in glycerol-based biofloc at LSD attained the highest (p < 0.05) serum superoxide dismutase (SOD), glutathione reductase (GR), and catalase than other experimental groups. Regarding the nonspecific immune status, significantly increased expression of CC-chemokines, CXC-chemokines, TLR7 and IL-8 genes was found in molasses based biofloc groups. The data of the present study revealed that using molasses promotes health status of Nile tilapia cultured in a biofloc system.

The application of biofloc to fish species has several advantages, including the enhancement of production by increasing growth performance and survival rate and the improvement of fish aquaculture physiological activity. There has been a recent increase in biofloc addition to fish culture, and this review examines changes this causes to the survival and growth rate of fish and its economic feasibility. Physiological activity and disease resistance of biofloc-fed fish is being extensively studied. The hematological parameters and antioxidant and immune responses of fish fed biofloc were reviewed in this study, as well as their disease resistance by testing them for major specific diseases. Standards for effectively applying biofloc to fish aquaculture are also suggested.