Biofloc Treatments Research Articles

Carbohydrate sources deferentially influence growth performances, microbial dynamics and immunomodulation in Pacific white shrimp (Litopenaeus vannamei) under biofloc system

This study aims to evaluate the influence of different carbohydrate sources on water quality, growth performance and immunomodulation in pacific white shrimp and to find an alternate for molasses in biofloc system. The experiment consists of 8 biofloc treatments with different carbon sources, C1 (maida flour), C2 (wheat flour), C3 (gram flour), C4 (millet flour), C5 (rice flour), C6 (corn flour), C7 (molasses), C8 (multigrain flour) and un-supplemented control C0 was conducted in 200 L tank system for 120 days. Shrimp juveniles of average weight 1 g were stocked at the rate of 300 nos/m3. Shrimp reared in C8, C7 and C4 treatments had similar growth, survival rate, and disease resistance and were significantly higher (P < 0.05) than other treatments including control. Immune parameters like total hemocyte count (THC) and prophenoloxidase (ProPO) activity showed significantly higher (P < 0.05) levels in biofloc treatment groups. The genes targeting the proPO cascade (PX, BGBP) and antioxidant defense systems (SOD, MnSOD, CAT) revealed significant upregulation in the transcript levels indicating an enhancement in the immune-regulatory functions in the BFT groups. The results suggest that millets and multigrain flour can effectively replace molasses as the carbohydrate source for biofloc system and the biofloc system offers higher growth, survival, and immunomodulation than control.

Influence of differential protein levels of feed on production performance and immune response of pacific white leg shrimp in a biofloc–based system

A130-day culture experiment was performed to compare the effects of rearing Litopenaeus vannamei in a biofloc system and conventional autotrophic system, supplemented with diets having graded protein levels on growth performance, non-specific immune response and immunomodulatory activity. The experiment groups consisted of four protein-level treatments with four replicates each, and was performed in 16 experimental units (7.5-Tcapacity) stocked with juvenile L. vannamei (initial average weight 1.48 ± 0.4 g) at a density of 150 juvenile shrimps /m3. Biofloc-based groups fed with supplementary feed containing varying levels of crude protein (CP) BFT40 (40% CP), BFT32 (32% CP) and BFT24 (24% CP), and a control group (CP 40%), were maintained in an autotrophic system. At the end of the experimental period, there was an improvement of 32.6–52.6% in terms of productivity, 22–27.6% average body weight; 8.7–19.6% survival rate and 10–31% feed conversion ratio (FCR) in shrimp maintained in biofloc systems as compared to control. Similarly, the protein efficiency ratio (PER) in biofloc treatment groups was32 to 83% higher than control. The shrimp also showed higher resistance to disease in the biofloc treatment when challenged with pathogenic Vibrio parahaemolyticus, as survival of juveniles was significantly higher (p < 0.05) in the biofloc treatments than in the control group. The total hemocyte count and proPhenoloxidase activity were significantly increased in the biofloc treatments when compared to control. The mRNA profiling of important immune genes in the shrimps showed higher levels of expression in the 32 and 40% CP feed treatments. Superoxide dismutase (SOD) mRNA transcript levels were highly up-regulated in the BFT40 treatment (7-fold), moderately upregulated in the BFT32 treatment (2-fold), and downregulated in the BFT24 treatment (0.9-fold). Transcription of antimicrobial peptides like crustin showed significant up-regulation in BFT40 (10.31-fold) followed by BFT32 (6.11-fold) and BFT24 (1.07-fold). Likewise, other immune genes, such as MnSOD, hemocyanin, proPhenoloxidase (proPO), peroxinectin (PX) and serine protease (SP) showed similar trends, indicating immunomodulation in the biofloc groups. We concluded that the biofloc system has the potential to improve growth performance, immune response and disease resistance in Pacific white shrimp in spite of the low-protein supplemented diet.

Biofloc technology (BFT) applied to tilapia fingerlings production using different carbon sources: Emphasis on commercial applications

The biofloc technology, can successfully use in tilapia fingerling commercial production with some benefits, nevertheless the studies are scarce. The objective was to determine the effect of the BFT system using different carbon sources on the productive parameters, demand of feed and water, in tilapia fingerlings (Oreochromis niloticus) production. The study was conducted at the company Centro Acuícola del Estado de Sonora, it was simple randomized with three treatments and one control (in triplicate). The treatments (carbon sources) were corn flour (CF), wheat flour (WF), sugar (SU) and a control (C) traditional system. The experiment was carried out in 12 glass fiber tanks (100 L) at a density of 3 ind/L (0.05 g/ind). The water quality, productive parameters, cost of consumed food and volume of used water were determined. At the end of the growing period, the lowest weight corresponded to WF (0.30 g/ind) and the highest to SU (0.44 g/ind) and C (0.41 g/ind). The FCR in biofloc treatments varied from 1.28 to 1.51, with no significant differences among them, whereas the 2.33 registered in C was significantly higher (P < .05). The control had the lowest protein efficiency (1.17), while the maximum was recorded in SU (2.11). Proximal tissue analysis showed a crude protein content of 63.9 to 71.0 g/100 g dry basis, with significant differences among treatments. The survival in the stress test was similar among treatments (98.3–99.3%). To produce a batch of 10,000 fingerlings, the used water in BFT was 6.1–7.8 m3 and 23.9 in the traditional system. The supplied feed in BFT varied from 5.8–6.3 kg/batch; meanwhile in the control it raised to 10.7 kg/batch. The cost of feed + C source was estimated in 6.53–7.80 USD/batch in BFT and of 9.13 USD/batch in the control. The fingerlings obtained in CF and SU treatments had a similar zootechnical performance to the control, but the savings in feed and water were significant.

Proteome modifications of Pacific white shrimp (Litopenaeus vannamei) muscle under biofloc system

The objective of the study was to examine the effects of biofloc technology on the muscle proteome of Litopenaeus vannamei. Two biofloc treatments and one control were compared: biofloc‐based tanks under zero‐water exchange fed with 150 g/kg crude protein (BF15), or with 250 g/kg crude protein (BF25) diets, and clear water tanks with 50% of daily water exchange stocked with shrimp fed with similar amount of a 250 g/kg crude protein diet, referred to as control. The shrimp (5.28 ± 0.42 g) were divided into the 300‐L fibreglass tanks (water volume of 200 L) at a density of 35 shrimp per tank and were cultured for 35 days. The biofloc groups displayed better growth and survival compared to the control. The muscle tissue from the control and BF25 groups was subjected to proteomic analysis. Lactate dehydrogenase, enolase, arginine kinase, mitochondrial ATP synthase subunit alpha, mitochondrial ATPase inhibitor factor 1 precursor, serpin 3 and myeloid differentiation factor 88 had an increased abundance in the BF25 group, while myosin heavy chain type 1 and myosin heavy chain type 2 showed a decreased abundance. The results indicate that biofloc technology could alter the expression of proteins involved in structure, metabolism and immune status of cultured shrimp.

Immuno-physiological response of Litopenaeus vannamei in oil palm kernel meal based biofloc systems

A 45-day experiment was conducted to assess the immuno-physiological response of Litopenaeus vannamei in oil palm kernel meal based biofloc systems. L. vannamei of average weight (0.82±0.02 g) were stocked in tanks at a stocking density of 300 PL/m3. Biofloc-based treatment obtained significantly better growth performance at the end of the experimental period. The stress parameters like SOD, CAT, LDH and GST were considerably lower in biofloc-based treatment as compared to the control. The oil palm based biofloc system showed lower AST and ALT values than the clear water control. The shrimp from biofloc treatment possessed significantly higher immune status as compared to control regarding the prophenol oxidase (proPO) activity. Biofloc treatment showed higher relative survival percentages than control. It indicates that oil palm kernel meal can be used as a potential carbon source for biofloc based shrimp culture.

Comparing biofloc, clear-water, and hybrid nursery systems (Part I): Shrimp (Litopenaeus vannamei) production, water quality, and stable isotope dynamics

Indoor, intensive, nursery-based recirculating aquaculture systems (RAS) can provide high-quality juvenile shrimp for indoor or pond-based production systems in a biosecure manner. However, it is unclear what type of RAS is most appropriate for indoor shrimp nurseries. This study compared three types of RAS nurseries: biofloc (BF), clear-water (CW), and hybrid (HY). Each treatment included four, randomly assigned 160 L (0.35-m2) tanks that were stocked with 3000 post-larvae shrimp m−3. The post-larvae (PL10) shrimp had an initial average weight of 7 ± 0.0 mg and were grown for 48 days. The BF tanks included external settling chambers as the only filtration mechanism. The CW tanks had settling chambers, foam fractionators, and external biofilters to fully clarify the water and process nitrogenous waste. Hybrid tanks included settling chambers, and external biofilters to maintain some suspended solids along with external biofiltration. Overall, the CW treatment had significantly higher dissolved oxygen (DO) and pH levels than the BF and HY systems. The HY treatment had significantly higher DO than the BF treatment. Nitrite concentration was significantly higher in the HY treatment than the CW treatment. Turbidity in the BF treatment was significantly higher than the other treatments. On the final sample date, the BF treatment had significantly higher nitrite and nitrate concentrations than the other treatments. Differences between treatments in terms of shrimp survival, mean harvest weight, specific growth rate, and feed conversion ratio were not significant. The final weight of the shrimp at 48 days for the BF, CW, and HY were 670 mg, 640 mg, and 590 mg respectively. A stable isotope mixing model indicated that, in the BF treatment, 13% of the C and 34% of the N in harvested shrimp tissue may have originated from biofloc material, signifying some nutrient recycling. The nitrification process was more effective with the inclusion of an external biofilter. All three system types appear suitable for RAS shrimp nursery production although consideration should be given to water quality consistency and filtration costs.

Effect of biofloc technology on water quality and feed utilization in the cultivation of gibel carp (Carassius auratus gibeliovar. CAS III)

This study was designed to use sucrose as carbon source to investigate the effect of biofloc technology on water quality and feed utilization in the cultivation of gibel carp (Carassius auratus gibelio var. CAS III). Three isolipidic and isoenergetic diets were formulated containing graded levels of dietary protein (257.4, 300.7 and 353.4 g/kg). The control group (P34) was fed with 353.4 g/kg protein diet without biofloc. Three biofloc treatments (P24 + B, P29 + B and P34 + B) were fed with the three diets with daily sucrose supplementation and continuous air inflation. The results found that the sucrose supplementation could generate biofloc and increased biofloc volume (BFV, p < 0.05). The concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO3-N) and the total phosphorus (TP) of all tanks decreased in biofloc groups, and the total nitrogen (TN) of P24 + B treatment tanks was significantly lower than that of the control group (p < 0.05). The growth of P24 + B and P29 + B group was similar with that of control group (p > 0.05). Feed conversion ratio (FCR) of P29 + B was lower than P24 + B and P34 + B (p < 0.05). Protein retention efficiency (PRE) of P24 + B group was significantly higher than other treatments (p < 0.05). Phosphorus retention efficiency (PhRE) of P24 + B group was the highest among all treatments. Compared with the control group, P29 + B group had an improved total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity and contained the lowest malondialdehyde level (MDA). The present results indicated that low-protein diet is more suitable for gibel carp in zero-water exchange biofloc system compared with high-protein diet.

Growth performance and robustness of African Catfish Clarias gariepinus (Burchell) in biofloc-based nursery production with different stocking densities

The aim of this research is to evaluate the effects of biofloc system application at different fish density on the nursery production performance and the robustness of African catfish Clarias gariepinus (Burchell) against Aeromonas hydrophila and salinity stress. An economic analysis was also performed to determine the most optimum fish density in biofloc‐based African catfish nursery production. African catfish with an average body weight of 0.96 ± 0.04 g and average body length of 4.20 ± 0.46 cm, respectively, were distributed in 12 units of circular plastic‐lined tanks (1,020 L). The experiment consisted of four treatments in triplicates, that is, a control without carbon source addition at a density of 4 fish/L, and three biofloc treatments at different densities, that is, BFT4 (4 fish/L), BFT6 (6 fish/L) and BFT8 (8 fish/L). Tapioca flour was used as the organic carbon source in biofloc systems and was added at an estimated C/N ratio of 10. Housing the fish in biofloc systems resulted in higher fish growth, more efficient feed utilization, higher fish robustness against A. hydrophila infection and salinity stress, as well as higher profitability of nursery production. Increasing the fish density resulted in higher mortality. However, higher number of fish produced and lower feed conversion ratio were observed in the treatments with higher density (6 and 8 fish/L). In conclusion, the application of biofloc technology at a density of 8 fish/L could be recommended to increase the production and profitability of African catfish nursery culture.

Nursery of young Litopenaeus vannamei post-larvae reared in biofloc- and microalgae-based systems

A 13-day nursery trial was conducted to evaluate the performance of young Litopenaeus vannamei post-larvae (from PL6 to PL18) reared in both biofloc and microalgae-based systems at a stocking density of 67 PLs L−1. The effects of different concentrations of total suspended solids (TSS) on PL performance were also evaluated. One experimental group was reared in a conventional microalgae-based system with daily water exchange and daily addition of microalgae (herein called microalgae treatment). The other two experimental groups were reared using biofloc technology (BFT) with daily dextrose addition and no water exchange, but in the “Biofloc-500” treatment, TSS were maintained at around 500mgL−1, while in the “Biofloc-700” treatment, TSS were maintained at around 700mgL−1. Water quality variables remained within the appropriate range for larval culture. In microalgae treatment, ammonia control was likely associated with its assimilation into microalgae biomass and daily water exchange. In biofloc tanks, however, the addition of dextrose stimulated the production of bacterial biomass from ammonia. This system required only 12.9% of the water used by the microalgae treatment since water was not exchanged during the culture. The nursery of young PLs resulted in similar (P>0.05) performance in all treatments: survival >94%, PL length ∼ 11.5mm, and PL dry weight ∼ 1.2mg. In addition, the salinity stress test (>90.0%) was not significantly different among treatments. Our results indicate that BFT can be as effective as the microalgae-based system for the nursery of young L. vannamei post-larvae. We also found that post-larvae performance was similar (P>0.05) between biofloc treatments, indicating that organisms can tolerate environments with large quantities of solids.

COMPARATIVE STUDY OF NITROGEN BIOREMOVAL FROM AQUACULTURE WASTEWATER USING BIOFLOCS TECHNIQUE (BFT) VERSUS BIOFILTRATION SYSTEM

Laboratory experiment aimed to comparison between treatment of fish wastewater using biofloc technology (BFT)and biofilter system to re-use water and reduce its change periods. Ammonium concentration increased from 0.51 mg/l at beginning of experiment to 0.54 mg/l and decreased to 0.25 mg/l and is fixed at 0.49 mg/l for biofilter samples. While, these concentrations ware 0.62- 0.87-0.12-0.27 mg/l for biofloc treatment samples. Ammonium reduction ratio of biofilter was 32% versus 17.33% for biofloc technique at beginning of experiment then it still increasing and reached to 42 % for biofilter against 7.45% of biofloc technique. Unexpected decrease in the ammonium reduction ratio for biofilter system by 21.87 and 15.52% versus 62.50 and 53.45% correspondingly for biofloc. These results were referred to biofiltration process adaptation and lack of uniformity of bioflocs throughout whole water tank. Results of measured ammonium concentrations show superiority of the use of biofloc technique over biofilter system. The decline in nitrite reduction ratio for biofilter of 63.16% at the second week of the start of experiment happened and then there was a slight increase in nitrite reduction ratio 63.49% to be settled on the 65% reduction ratio value. This was referred to biofilter clogging and biomass accumulation. Biofloc technique demonstrated an excessive superiority (93.02%) in nitrite reduction ratio at beginning of the experiment over biofilter system (70.54%). Two systems had similar behavior of nitrite reduction ratio throughout the rest of experiment. Finally, use of BFT systems to freshwater tilapia aquaculture benefits both the reduction in ammonium and nitrite concentrations and can be effective in improvement fish production.

Effects of carbon sources and plant protein levels in a biofloc system on growth performance, and the immune and antioxidant status of Nile tilapia (Oreochromis niloticus)

The efficacy of different biofloc treatments (BFTs) to compensate for a reduction in dietary protein level under zero-water exchange systems was studied during a 10 weeks experiment, assessing the effect on water quality, growth, immune and antioxidant status of Nile tilapia (Oreochromis niloticus) fingerlings. Six groups were established and fed the same plant-based feed containing 20 or 30% crude protein: two groups in clear water conditions with no added carbon source, two biofloc groups given a wheat milling by-product (WMB) as additional carbon source and two biofloc groups given rice bran (RB). The results showed that biofloc volume was higher when WMB was used as carbon source. The highest growth performance were obtained with the biofloc system and the higher dietary protein level. Fish fed 20% crude protein and stocked in WMB biofloc significantly outperformed the fish fed 30% crude protein and stocked in clear water. Significant improvements in hematocrit, white blood cells, lymphocytes, plasma proteins, and humoral (immunoglobulin, lysozyme, myeloperoxidase and ACH50) and cellular (phagocytosis activity and respiratory burst) immune parameters were observed in all BFT fish. BFT also increased superoxide dismutase and catalase activities. Moreover, the fish fed 20% dietary protein and reared in both biofloc conditions showed equal or superior levels of the immunological criteria to fish fed 30% protein in clear water conditions. In conclusion, using WMB as carbon source could make up for a reduction in dietary protein levels of 10% and improve growth performance, and the immune and antioxidant status of O. niloticus.

Effect of molasses addition at C:N ratio of 20:1 on the water quality and growth performance of giant freshwater prawn (Macrobrachium rosenbergii)

A 90-day experiment consisting of two groups, a biofloc treatment and a control treatment, was performed in six indoor cement ponds to investigate the effectiveness of biofloc technology (BFT) for maintaining water quality and growth performance of Macrobrachium rosenbergii in a zero-exchange water system. Molasses was added to the biofloc ponds with the C/N ratio of 20:1 based on the amount of daily feed. The floc volume in the biofloc group increased gradually (28.72 mL L−1) along with molasses addition, but the value in the relative control group remained at low levels (0.40–4.97 mL L−1) (P < 0.05). A total of 4.97% Bacillus, 4.20% Lactococcus, and 9.65% Nitrospira were determined in the biofloc water, and these values were significantly higher than that in the control water (P < 0.05). Ammonia-N, nitrite-N, nitrate-N, and total nitrogen concentrations in the biofloc water were significantly lower than that in the relative control group (P < 0.05). Potassium orthophosphate (PO4−-P) and total phosphorous (TP) concentrations increased consistently in both groups. The same-day value of PO4−-P concentration in the control group (6.37–12.96 mg L−1) was 1.5 higher than that of the biofloc group (4.66–7.99 mg L−1) from day 60 to day 90 (P < 0.05). Significant differences in TP concentration (P < 0.05) were noted between the control and biofloc groups from the 15th day to the 30th day and from the 60th day to the 90th day. The biofloc treatment resulted in a 10.62% higher survival rate, a 27.55% higher weight gain rate, and a 7.13% higher specific growth rate (P < 0.05). The findings of the present study demonstrated that BFT effectively promoted water quality, as well as growth and survival of M. rosenbergii, by regulating the inorganic nitrogen and phosphorus dynamics.

Comparing clear-water RAS and biofloc systems: Shrimp (Litopenaeus vannamei) production, water quality, and biofloc nutritional contributions estimated using stable isotopes

Indoor shrimp aquaculture systems can be used to produce fresh, never-frozen, quality shrimp near metropolitan seafood markets regardless of season and climate. However, questions still remain regarding what type of production system is best suited to maximize indoor production. In this project, two types of systems were compared: clear-water (CW) RAS and biofloc (BF) systems. Three, 1.36m3 tanks were assigned to each of the two treatments; CW tanks had external settling chambers, two foam fractionators, and external biofilters, all operated continuously. BF tanks had settling chambers and one foam fractionator which were operated as needed to control solids accumulation. Shrimp weighing 0.42g were stocked in all tanks at 250m−3 and grown for 55 days. Ammonia and pH levels were significantly (P<0.05) higher in the CW treatment, while nitrite, nitrate, and turbidity were all significantly higher in the BF treatment, although all parameters remained within acceptable ranges for shrimp growth. Shrimp mean harvest weight was significantly higher, biomass (kgm−3) was significantly greater, and FCR was significantly lower in the CW treatment; there were no significant differences in survival between treatments. Isotope levels indicated that shrimp in the BF treatment obtained a portion of the C (18-60%) and N (1-18%) in their tissues from biofloc material; however, this effect did not positively influence production in that treatment. By nearly eliminating solids from the water and using an external biofilter, substantially better water quality was maintained in the CW systems, which may have been a major contributor to the improved shrimp production in that treatment.

Enhanced growth and immuno-physiological response of Genetically Improved Farmed Tilapia in indoor biofloc units at different stocking densities

An experimental trial was conducted for 90 days to evaluate the growth performance, immunophysiological response of GIFT strain of Tilapia in biofloc-based rearing system and to assess the relative percentage survival in 3 days after challenging with the virulent strain of Aeromonas hydrophila. Fingerlings with an average body weight 0.98 ± 0.06 g were stocked in triplicate at different stocking densities of 200 (SD1), 250 (SD2), 300 (SD3) and 350 (SD4) m−3 in biofloc-based treatments and 150 (C) m−3 in control (clear water). Biofloc-based units (SD1 and SD2) obtained significantly better (P < 0.05) growth performances at the end of the experimental period. Mean body weight of fish in biofloc-based units showed a decreasing trend with increase in stocking density with 100% survival in all units including control. The stress parameters were significantly lower in biofloc-based rearing units especially in treatments SD1 and SD2 as compared to the control. The fish from the biofloc-based units (SD1 and SD2) possessed significantly (P < 0.05) higher immune status as compared to control and other biofloc treatments in terms of respiratory burst, serum lysozyme and myeloperoxidase activity. Relative survival percentages were significantly better in biofloc treatments with highest in SD1 and SD2 (83.33%) after challenge study. GIFT strain of Tilapia at higher stocking densities 200–250 nos m−3 can be taken as optimum stocking density whereas higher stocking densities up to 350 nos m−3 can be reared in the biofloc systems without compromising the growth and immunity.

Effects of Different Carbon Sources on Bioactive Compound Production of Biofloc, Immune Response, Antioxidant Level, and Growth Performance of Litopenaeus vannamei in Zero‐water Exchange Culture Tanks

AbstractThis study aimed to investigate the development and bioactive compounds of biofloc promoted by adding molasses and wheat bran to zero‐water exchange culture tanks and their effects on physiological parameters and growth performance of juvenile Litopenaeus vannamei (initial weight: 6.8 ± 0.4 g). Different combinations of molasses and wheat bran were added as carbon sources: T1, 100% molasses; T2, 50% molasses + 50% wheat bran; T3, 25% molasses + 75% wheat bran. Clear water tanks with water exchange served as the control group (control). After the 30‐d experiment, the development of biofloc in terms of total suspended solids (TSS) and biofloc volume (BFV) showed significant differences in the three biofloc treatments, especially the highest levels of TSS and BFV observed in T3. The levels of poly‐beta‐hydroxybutyrate or polysaccharide in the biofloc of T1 and T2 were significantly higher than those in T3. Meanwhile, compared with the control group, most of the immune and antioxidant parameters and growth performance of shrimp were significantly enhanced in biofloc treatments, especially in T1 or T2. In conclusion, different carbon sources could effectively affect the development and bioactive compounds of biofloc, which could improve physiological health status and growth performance of shrimp in zero‐water exchange systems.

Contribution of bioflocs to the culture of Litopenaeus vannamei post-larvae determined using stable isotopes

The aim of this study was to use preselected quality indicators for Litopenaeus vannamei post-larvae and the stable isotopes technique with δ13C and δ15N to determine the influence of bioflocs in shrimp feeding during the nursery phase, between PL1 and PL30. A control treatment (CT) with water renewal was compared to a biofloc treatment (BT) that received organic carbon fertilizations. Different types of commercial feed (Stresspak and Flake-INVE™, PL40-GUABI™), microalgae (Chaetoceros muelleri) and Artemia sp. nauplii were used as food sources. The physical and chemical parameters of water and ammonia were monitored daily, and nitrite, nitrate and alkalinity were measured weekly. Suspended solids and the microorganisms of bioflocs were characterized. At the end of the experiment, fifteen shrimps of each replicate were collected to evaluate nine larvae quality indicators. Isotopic values of 13C and 15N of food sources and shrimp tissues were collected on days 10, 20 and 30, and a Bayesian model of isotopic mixture measured the contributions of these sources to the shrimp biomass. Salinity, alkalinity and nitrite differed significantly between the treatments but were appropriate for post-larvae production. The larvae quality conditions in the CT treatment were ranked as “good,” whereas the BT conditions were considered “excellent” according to the analysis of larval quality parameters. The stable isotopes analysis showed that the PL40 GUABI™ feed was the most important food source throughout the experimental period in the CT. In the BT (10th and 20th days), the bioflocs and commercial feeds (Flake-INVE™, PL40-GUABI™) did not present significant variations in their contribution ratios; however, on the 30th day, the contribution of the PL40-GUABI™ feed was higher when compared to bioflocs. In general, the commercial feed played a more important role as a food source for Litopenaeus vannamei larvae during the nursery phase, although the consumption of bioflocs led to a better larvae quality.

Nursery performance of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) cultivated in a biofloc system: the effect of adding different carbon sources

Effect of different carbon sources on nursery performance of Pacific white shrimp (Litopenaeus vannamei) cultivated in biofloc system was investigated. Shrimp postlarvae (98.47 ± 8.6 mg) were fed for 32 days in tanks with water volume of 130 L and density of 1 individual L−1. One control treatment and four biofloc treatments (BFT1, BFT2, BFT3 and BFT4) with adding different carbon sources including molasses, starch, wheat flour and mixture of them, respectively, were considered at equal weight ratios. According to the results, salinity, dissolved oxygen and pH were not significantly different among the biofloc treatments (P > 0.05). Maximum pH (8.27) and maximum dissolved oxygen (6.35 mg L−1) were recorded in the control. Maximum (0.43 mg L−1) and minimum (0.09 mg L−1) ammonia were recorded in the control and BFT2, respectively (P < 0.05). Using simple carbohydrates (molasses and starch) lowered the ammonia concentration significantly. The highest increase in body weight (1640.43 ± 231.28 mg), growth rate, specific growth rate (8.97 ± 0.42% per day) and biomass (190.29 ± 26.83 mg) were found in BFT1 and the highest survival (90 ± 0.77%) was found in BFT4. The highest feed conversion (1.52 ± 0.23) and the lowest feed efficiency (66.81 ± 7.95) were observed in the control (P < 0.05). The proximate composition analysis revealed an increase in lipid and ash in biofloc treatments. Results indicated that using biofloc technology with zero-water exchange system and adding carbon sources could help to recycle waste and improve the water quality. Moreover, the type of carbonaceous organic matter as a substrate for heterotrophic bacteria would be effective in degradation and metabolization of ammonia and nitrite.

Role of Biofloc in the Growth and Survival of Blue morph, &lt;I&gt;Pseudotropheus saulosi&lt;I&gt;

Objective: To evaluate the effect of biofloc on the growth and survival of ornamental cichlid, Blue morph. Methods/Statistical analysis: Thousand number of Blue morph were stocked in circular cement tanks of 14000 l capacity in control and biofloc rearing tanks. Various water quality parameters, qualitative and quantitative parameters of biofloc and growth parameters were estimated periodically. The results were statistically analysed using ANOVA. Results/Findings: All the water quality parameters were high in Control tank compared to biofloc. Floc volume was higher in biofloc tank (4.4 mg/l). The number of microorganisms present in biofloc was much higher than Control. The survival rate of Blue morph young ones in biofloc treatment was 93% and it was 90.2%in control.All growth parameters expect length, weight gain and mean length were significantly significant (P<0.01) among the days of culture as well as between control and biofloc treatment tanks. Conclusion: Biofloc increased the growth and survival of Blue morph significantly.

Growth, non-specific immunity and disease resistance of Labeo rohita against Aeromonas hydrophila in biofloc systems using different carbon sources

A 60day growth trial was carried out to evaluate biofloc based rearing system for Labeo rohita fingerlings. The C/N ratio of 15 was maintained in four biofloc treatments (T1, T2, T3 and T4) using indirect and long-lasting carbon sources (tapioca, wheat, corn and sugar bagasse) along with one control (C). Each group consisted of triplicate tanks and each tank was stocked with 50 fingerlings (4.80g±0.12) of L. rohita. Fishes were challenged with A. hydrophila 60days post rearing and relative percentage survival (RPS) was recorded over 14days post challenge. Serum samples were collected on 20, 40 and 60days interval of sampling for the evaluation of non-specific immune and stress parameters. The results revealed that fishes reared in tapioca based biofloc system showed significantly (p<0.05) higher serum protein, serum albumin, total immunoglobulin, respiratory burst activity, myeloperoxidase activity and lower serum glucose and serum cortisol when compared to wheat, corn, sugar bagasse based biofloc system and control. Growth, feed conversion ratio (FCR), feed efficiency ratio (FER), and specific growth rate (SGR) of fishes in the biofloc treatments were significantly better (p<0.05) than control. Tapioca based biofloc treatment showed significantly (p<0.05) higher RPS (66.66%) than other treatments. The study suggests that the fishes reared using in-situ biofloc produced by tapioca can enhance growth and non-specific immune responses under zero water exchange system and hence ensures sustainability. Statement of relevance•Zero water exchange reduces water scarcity and pollution problems•Improves welfare of the animals by stimulating immunity and protection against diseases•In-situ production of valuable microbial protein thus reducing dependence on fishmeal.

C:N ratios affect nitrogen removal and production of Nile tilapia Oreochromis niloticus raised in a biofloc system under high density cultivation

Over a six-month trial, growth performance of juvenile tilapia Oreochromis niloticus, raised under biofloc cultivation, was recorded. Five treatments with three replicates and 237 juveniles per replicate at different C:N ratios were tested (10:1, 12.5:1, 15:1, 17.5:1, 20:1). Molasses was added every fourth day as the carbon source. Trials were performed in eighteen 3.14m3 circular tanks with constant aeration. Survival in all treatments with biofloc was similar and significantly higher (94.60±2.03%) than in the control treatment (84.96±1.53%). Best weight gain (g/day) occurred in the control treatment, but was influenced by low density. The 10:1 and 15:1 C:N treatments had similar weight gains, but not the 12.5:1 and 17.5:1 C:N treatments. Total production in the 10:1 ratio treatment was the highest (18.03±0.25kgm−3), with slightly declining production, in this order: control (17.86±0.16), 15:1 (17.73±0.18), 12.5:1 (17.20±0.28), 17.5:1 (16.44±0.04), and 20:1 (16.28±0.02). Water quality remained similar in all biofloc treatments, but lower concentrations of nitrogen compounds occurred in the 10:1 C:N ratio tanks. These results suggest a 10:1 C:N ratio provides good survival and growth of tilapia with no water exchange. Biofloc technology is a good strategy in areas where alkaline pH is a limiting factor for aquaculture activities because the pH decreases gradually as molasses is added. Statement of RelevanceThe success and permanence of aquaculture sector relies on the implementation of sustainable and environment-friendly technology, the BFT optimizes energy and resources during production, so our results contribute significantly to the sector.