**7.3 Applications of biofloc as complemented food in aquaculture**

BFT has been successfully used for culture of fish and shrimp, such as tilapia, carp, and *L. vannamei*. Results showed that BFT increased individual fish weight,

weight gain, and protein efficiency ratio of tilapia by 12.54, 9.46, and 22.2%; decreased feed conversion rate (FCR) by 17.5% [66]; elevated total weight gain and specific growth rate increase by 128% and 112% [67], respectively; and also significantly increased the final weight, weight gain, and length of *L. vannamei* [37, 63]. And those results for enhancing growth of fish and shrimp are mainly contributed to biofloc. Research from Tierney and Ray [2] revealed that the shrimp in the BFT treatment received an estimated 87% of their carbon and 66% of their nitrogen from the pelleted feed source, whereas the rest of 13% and 34% came from the

*Compositions of biofloc produced from different feedstuff and carbon sources.*

**Animals Carbon sources Feedstuff**

*DOI: http://dx.doi.org/10.5772/intechopen.88993*

Mixture of molasses, starch, and wheat flour with equal weight ratio **composition**

*L. vannamei* Molasses and wheat bran 42.5 – 20:1 28.7–43.1 2.11–3.62 [59]

*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ*

Tilapia Wheat flour 24 6.23 – 37.93 3.16 [61]

*Labeo rohita* Wheat flour 29.6–35.4 4.2–16.5 10:1 35.4 1.1 [52]

Catfish Glycerol 43 6 10:1 44.27 5.84 [64]

**C:N Biofloc**

**CP CL CP CL**

35 6.24 38.41 3.23

35 119 8.4:1 53.5 1.9

35 – – 18.4 0.3 [63]

15:1 38.65 7.35 20:1 32.64 10.78

Feed 22 12.3 11.6:1 50.6 2.6 [62]

Poly-β-hydroxybutyric 30 4 – 34.06 6.58 [34] Glucose 38.53 6.06

Molasses and wheat bran 40 13.1 20:1 30.4 0.47 [37]

Wheat flour 40 – 10:1 24.3 3.53 [53]

Glucose 20.37 2.45 15:1 32.29 4.19 [65]

Sucrose 28.04 4.30 Starch 21.67 3.83

Glucose 27.27 4.25 Sucrose 27.48 3.89 Starch 21.23 3.76

Sucrose 35–40 7–9 – 24.01 3.31 [60] Molasses 38 9 15:1 27.43 0.86 [28] Starch 23.1 1.14 Wheat flour 30.73 2.18

**composition**

25.46 1.24

**Ref.**

biofloc, respectively.

*Farfantepenaeus paulensis*

*Penaeus monodon*

Green cucumber

White cucumber

**Table 1.**

**13**

*Note: CP, crude protein; CL, crude lipid.*

#### **Figure 6.**

*Bioflocs observed with a light microscope. The minimal scale of the rule in the down part of the figure represents 25 μm. Arrows indicate free zooplanktons (a), and zooplanktons prey food from biofloc (b).*


*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ DOI: http://dx.doi.org/10.5772/intechopen.88993*

#### **Table 1.**

parts of the whole. In other words, most of the bioflocs remain in the water body, which may be an obstacle for growth of fish and shrimp. For alleviating the negative effect of biofloc on animal growth, excessive parts should be collected from water body and could be taken as an alternative protein source for preparing feedstuff. Even more, biofloc is fed to fish or shrimp as feedstuff directly due to its whole and

*Emerging Technologies, Environment and Research for Sustainable Aquaculture*

Nutritional value of biofloc is important for its reuse. However, this value is affected by several factors. Because the development of biofloc is sponsored and prompted by accumulation of ammonia and addition of carbon source, it is suspected that feedstuff and carbon source [30], especially the last one, would impressively affect biofloc nutritional composition and value (**Table 1**). For example, protein content and oil content of feedstuff will affect those of in biofloc. With regard to carbon source, there are two main types of carbon sources: (i) simple structure carbon sources with easily dissolving ability in water, such as glucose, sucrose, and sodium acetate [17, 20], and (ii) complex compounds, like flour or bran of rice and wheat [56] and brewery residues, which are a by-product from beer production industry [22]. In general, complex carbon source is more difficult to dissolve and more powerful in improving biofloc nutritional value, which in turn improves the growth of fish or shrimp [17, 20]. This carbon source is not easy to degrade with big diameter so that animals in water could easily prey and eat them directly; thus, except for being used as carbohydrate, those materials also contain other nutritional materials essential for growth of fish and shrimp, such as proteins,

high nutritional value.

**Figure 6.**

**12**

**7.2 Factors influencing nutritional value of biofloc**

oils, vitamins, and minerals, even carotenoids [57, 58].

**7.3 Applications of biofloc as complemented food in aquaculture**

BFT has been successfully used for culture of fish and shrimp, such as tilapia, carp, and *L. vannamei*. Results showed that BFT increased individual fish weight,

*Bioflocs observed with a light microscope. The minimal scale of the rule in the down part of the figure represents*

*25 μm. Arrows indicate free zooplanktons (a), and zooplanktons prey food from biofloc (b).*

*Compositions of biofloc produced from different feedstuff and carbon sources.*

weight gain, and protein efficiency ratio of tilapia by 12.54, 9.46, and 22.2%; decreased feed conversion rate (FCR) by 17.5% [66]; elevated total weight gain and specific growth rate increase by 128% and 112% [67], respectively; and also significantly increased the final weight, weight gain, and length of *L. vannamei* [37, 63]. And those results for enhancing growth of fish and shrimp are mainly contributed to biofloc. Research from Tierney and Ray [2] revealed that the shrimp in the BFT treatment received an estimated 87% of their carbon and 66% of their nitrogen from the pelleted feed source, whereas the rest of 13% and 34% came from the biofloc, respectively.

When bioflocs were eaten directly by fish or shrimp, the protein utilization efficiency of feed elevated by 29% [68], and the FCR decreased by about 18% for tilapia [66, 67], and also decreased for *Penaeus monodon* [69]. It is found that the protease, lipase, and amylase activities in the intestine, liver, and stomach of tilapia [66, 67] and *L. vannamei* were all significantly raised [25], which improves the digestion and intake of feed. A large number of heterotrophic bacteria are located in biofloc, most of which will secret enzymes like protease, lipase, and amylase, indicating that preying on biofloc would directly increase the content of those enzymes in digestive organs of fish and shrimp. Those bacteria also would secret digestive enzymes in vivo after entering, colonizing and propagating in the intestine [25]. In a BFT system for culturing *L. vannamei*, the feedstuff containing 35% of protein could be altered with feedstuff whose protein content decreased to 25%, because most nutrition materials lacking in low protein content feed could be compensated from biofloc. In another way, about 25% feedstuff could be saved when culturing *L. vannamei* with BFT because biofloc was hunted as a food in situ [54]. It is even reported that no feed should be added in some BFT systems for culturing *L. vannamei* and *Macrobrachium rosenbergii* [18, 37].

aquaculture including multitrophic aquaculture is also an alternative, in which byproducts (wastes) from one species are recycled to become inputs (fertilizers, food,

*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ*

From this point of view, in practical aquaculture operations, BFT utilizes byproducts from agriculture industries, such as cassava meal [22], molasses [26–28], tapioca [29], wheat bran [25, 31], rice bran [20, 29], and brewery residues [22], as fertilizers for assimilating organic and inorganic materials. And in turn, its own byproduct, biofloc, becomes complemented food for aquatic suspension or deposit feeders, like herbivorous fish. Some omnivorous aquatic animals, such as shrimp and tilapia, were all very suitable to be cultured with BFT [44, 62]. Due to the characteristics of in situ treatment of water quality and supplying of organic biofloc food, aquaculture systems that adopted BFT only need a few water exchange, even no water exchange, and decrease artificial feedstuff inputs, indicating reduced eutrophication risks of environment and the use of wild fish for aquaculture feeds

Rego et al. [74] analyzed the financial viability of inserting the BFT system (625 m<sup>2</sup> each pond) and maintaining the conventional culture system (2.86 ha each pond) for the marine shrimp *L. vannamei* in a farm located in the state of Pernambuco, northeastern Brazil. The total production costs of BFT were eight times higher than the conventional system. However, operating profit and profitability index were US\$ 51,871.54 per hectare per year and 30.22% for BFT, and US\$ 21,523.83 and 59.79% for the conventional system, respectively. In an investment analysis, indicators were favorable for both systems, with greater expressiveness of the net present value (NPV) for the BFT (US\$ 142,004.42) and internal rate of return (IRR) 4.5 times higher for conventional system (131.86%). When the cash flows were designed for 10 years to the discount rates of 10, 13, and 16%, the BFT system showed greater sensitivity to changes in rates, reducing significantly the NPV when interest rates increased. Risk was only observed in the BFT system, with up to 15% of probability when subjected to the discount rate of 16%. Both shrimp production systems represent a significant investment alternative for the rural sector in northeastern Brazil, because even from the perspective of risk management, the IRR has 90% probability ranging from 7.66 to 59.40% for the BFT and from 67.96 to 201.03% for the conventional

Undoubtedly, BFT is a novel solution for transformation of ammonia in aquaculture. However, how to effectively reuse or deposit biofloc, the by-product of assimilation of ammonia in BFT system in situ, as a supplemental food for aquatic

The consumed efficiency of biofloc by fish or shrimp in situ is not adequate high, resulting in gradual accumulation of TSS in BFT system because of huge numerous organic materials produced by blooming growth of heterotrophic bacteria. Thus, the causes contributed to this low efficiency should be researched. Furthermore, the strategies for improving the utilization efficiency of biofloc should be assessed as well, such as improving accumulation of lipid of biofloc, which will increase the nutritional value. Usually, the total lipid content in biofloc is too low to be sufficient for demand of fish and shrimp (**Table 1**). Previous studies found that the lipid contents of biofloc were 0.5–0.6% [63, 70], 1.03% [66], or 4.0% [62], respectively,

and energy) for another [73].

*DOI: http://dx.doi.org/10.5772/intechopen.88993*

to reserve balance of ecosystem.

systems [75].

**15**

**8.2 Practical application of BFT for economical benefits**

**8.3 Further improvements for reuse of biofloc**

animals, needs more researches in detail.

Biofloc is also used as an alternative protein source for fishmeal sometimes. The protein content in biofloc is evidenced to be very high, in general 25–40% [34, 63, 66, 70], in a case even up to 50% [62]. The essential amino acids were also rich in biofloc, and its composition was also highly in agreement with that in the fish body [71], indicating that it is valuable for growth of fish and shrimp. Dantas et al. [46] and Kuhn et al. [48] replaced 30% of fishmeal or soy meal with biofloc to manufacture feedstuff for feeding of *L. vannamei*, and results showed that the growth of shrimp is not affected. Kuhn et al. [47] thought that the whole soy meal could be replaced with biofloc and 67% for fishmeal. However, only appropriate replacement of fishmeal with biofloc could prompt the growth of shrimp obviously, approximately 15.16–16.5% [49].

In some cases, biofloc was collected and dried to make pellets and then fed to fish or shrimp like artificial or formulated feedstuff. Carps, *Labeo rohita*, and *L. vannamei* was cultured successfully with biofloc pellets according to a replacement ratio of 25, 50, and 50% to formulated feedstuff, respectively, without any negative effects on their growth [50–52]. However, when feedstuff was replaced 35% with biofloc, the growth of *L. vannamei* appears to be the fastest [72]. In fact, a replacement ratio lower than 10% could improve the growth of animals [55]. For example, when the replacement ratio was 4 and 8%, the individual mean body weight of *P. monodon* increased by 16.9 and 13.9%, respectively [53].

#### **8. Prospects**

Meeting future demand for fish is very important for global food security. However, barriers to growth have to be explicitly recognized to the environmental and economic pillars of sustainability [73]. Fortunately, BFT could fulfill those requests for sustainable development of aquaculture.

#### **8.1 Environmental advantages of BFT for sustainable development of aquaculture under framework of the FAO**

Except availability of land and water, environmental impact is another possible main constraint to aquaculture growth. Thus, aquaculture systems that reduce eutrophication risks and other environmental costs while providing income and extended social benefits should be developed [73]. For this purpose, the FAO thinks that herbivorous and omnivorous species should be promoted and integrated

*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ DOI: http://dx.doi.org/10.5772/intechopen.88993*

aquaculture including multitrophic aquaculture is also an alternative, in which byproducts (wastes) from one species are recycled to become inputs (fertilizers, food, and energy) for another [73].

From this point of view, in practical aquaculture operations, BFT utilizes byproducts from agriculture industries, such as cassava meal [22], molasses [26–28], tapioca [29], wheat bran [25, 31], rice bran [20, 29], and brewery residues [22], as fertilizers for assimilating organic and inorganic materials. And in turn, its own byproduct, biofloc, becomes complemented food for aquatic suspension or deposit feeders, like herbivorous fish. Some omnivorous aquatic animals, such as shrimp and tilapia, were all very suitable to be cultured with BFT [44, 62]. Due to the characteristics of in situ treatment of water quality and supplying of organic biofloc food, aquaculture systems that adopted BFT only need a few water exchange, even no water exchange, and decrease artificial feedstuff inputs, indicating reduced eutrophication risks of environment and the use of wild fish for aquaculture feeds to reserve balance of ecosystem.

#### **8.2 Practical application of BFT for economical benefits**

Rego et al. [74] analyzed the financial viability of inserting the BFT system (625 m<sup>2</sup> each pond) and maintaining the conventional culture system (2.86 ha each pond) for the marine shrimp *L. vannamei* in a farm located in the state of Pernambuco, northeastern Brazil. The total production costs of BFT were eight times higher than the conventional system. However, operating profit and profitability index were US\$ 51,871.54 per hectare per year and 30.22% for BFT, and US\$ 21,523.83 and 59.79% for the conventional system, respectively. In an investment analysis, indicators were favorable for both systems, with greater expressiveness of the net present value (NPV) for the BFT (US\$ 142,004.42) and internal rate of return (IRR) 4.5 times higher for conventional system (131.86%). When the cash flows were designed for 10 years to the discount rates of 10, 13, and 16%, the BFT system showed greater sensitivity to changes in rates, reducing significantly the NPV when interest rates increased. Risk was only observed in the BFT system, with up to 15% of probability when subjected to the discount rate of 16%. Both shrimp production systems represent a significant investment alternative for the rural sector in northeastern Brazil, because even from the perspective of risk management, the IRR has 90% probability ranging from 7.66 to 59.40% for the BFT and from 67.96 to 201.03% for the conventional systems [75].

#### **8.3 Further improvements for reuse of biofloc**

Undoubtedly, BFT is a novel solution for transformation of ammonia in aquaculture. However, how to effectively reuse or deposit biofloc, the by-product of assimilation of ammonia in BFT system in situ, as a supplemental food for aquatic animals, needs more researches in detail.

The consumed efficiency of biofloc by fish or shrimp in situ is not adequate high, resulting in gradual accumulation of TSS in BFT system because of huge numerous organic materials produced by blooming growth of heterotrophic bacteria. Thus, the causes contributed to this low efficiency should be researched. Furthermore, the strategies for improving the utilization efficiency of biofloc should be assessed as well, such as improving accumulation of lipid of biofloc, which will increase the nutritional value. Usually, the total lipid content in biofloc is too low to be sufficient for demand of fish and shrimp (**Table 1**). Previous studies found that the lipid contents of biofloc were 0.5–0.6% [63, 70], 1.03% [66], or 4.0% [62], respectively,

When bioflocs were eaten directly by fish or shrimp, the protein utilization efficiency of feed elevated by 29% [68], and the FCR decreased by about 18% for tilapia [66, 67], and also decreased for *Penaeus monodon* [69]. It is found that the protease, lipase, and amylase activities in the intestine, liver, and stomach of tilapia [66, 67] and *L. vannamei* were all significantly raised [25], which improves the digestion and intake of feed. A large number of heterotrophic bacteria are located in biofloc, most of which will secret enzymes like protease, lipase, and amylase, indicating that preying on biofloc would directly increase the content of those enzymes in digestive organs of fish and shrimp. Those bacteria also would secret digestive enzymes in vivo after entering, colonizing and propagating in the intestine [25]. In a BFT system for culturing *L. vannamei*, the feedstuff containing 35% of protein could be altered with feedstuff whose protein content decreased to 25%, because most nutrition materials lacking in low protein content feed could be compensated from biofloc. In another way, about 25% feedstuff could be saved when culturing *L. vannamei* with BFT because biofloc was hunted as a food in situ [54]. It is even reported that no feed should be added in some BFT systems for

*Emerging Technologies, Environment and Research for Sustainable Aquaculture*

Biofloc is also used as an alternative protein source for fishmeal sometimes. The protein content in biofloc is evidenced to be very high, in general 25–40% [34, 63, 66, 70], in a case even up to 50% [62]. The essential amino acids were also rich in biofloc, and its composition was also highly in agreement with that in the fish body [71], indicating that it is valuable for growth of fish and shrimp. Dantas et al. [46] and Kuhn et al. [48] replaced 30% of fishmeal or soy meal with biofloc to manufacture feedstuff for feeding of *L. vannamei*, and results showed that the growth of shrimp is not affected. Kuhn et al. [47] thought that the whole soy meal could be replaced with biofloc and 67% for fishmeal. However, only appropriate replacement of fishmeal with biofloc could prompt the growth of shrimp obviously, approximately 15.16–16.5% [49]. In some cases, biofloc was collected and dried to make pellets and then fed to fish or shrimp like artificial or formulated feedstuff. Carps, *Labeo rohita*, and *L. vannamei* was cultured successfully with biofloc pellets according to a replacement ratio of 25, 50, and 50% to formulated feedstuff, respectively, without any negative effects on their growth [50–52]. However, when feedstuff was replaced 35% with biofloc, the growth of *L. vannamei* appears to be the fastest [72]. In fact, a replacement ratio lower than 10% could improve the growth of animals [55]. For example, when the replacement ratio was 4 and 8%, the individual mean body weight of *P.*

Meeting future demand for fish is very important for global food security. However, barriers to growth have to be explicitly recognized to the environmental and economic pillars of sustainability [73]. Fortunately, BFT could fulfill those

Except availability of land and water, environmental impact is another possible

main constraint to aquaculture growth. Thus, aquaculture systems that reduce eutrophication risks and other environmental costs while providing income and extended social benefits should be developed [73]. For this purpose, the FAO thinks that herbivorous and omnivorous species should be promoted and integrated

**8.1 Environmental advantages of BFT for sustainable development of**

culturing *L. vannamei* and *Macrobrachium rosenbergii* [18, 37].

*monodon* increased by 16.9 and 13.9%, respectively [53].

requests for sustainable development of aquaculture.

**aquaculture under framework of the FAO**

**8. Prospects**

**14**

which were all lower than the demands for lipid of aquatic animals [8]. For example, the recommended total lipid level in the diet for shrimp is in general higher than 6.5% [4]. Although external equipment could be used to settle the excessive part of biofloc, how to treat this deposit containing high content organic matter and bacteria, part of which may be pathogens, was also a problem [39].

**Appendices and nomenclature**

*DOI: http://dx.doi.org/10.5772/intechopen.88993*

C:N (P) carbon to nitrogen (to phosphorus) ratio

*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ*

DMPT s,s-dimethyl-β-propionic acid thetine FAO Food and Agriculture Organization

BFT biofloc technology

FCR feed conversion rate IRR internal rate of return LC50 median lethal concentration

NPV net present value

**Author details**

Hai-Hong Huang

**17**

College of Life and Environmental Science, Hunan University of Arts and Science, Key Laboratory of Health Aquaculture and Product Processing in Dongting Lake Area, Zoology Key Laboratory of Hunan Higher Education, Changde, China

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: shinkanh@nwsuaf.edu.cn

provided the original work is properly cited.

NRC National Research Council PHB poly-β-hydroxybutyric ppm part(s) per million TAN total ammonia nitrogen TMAO trimethylamine oxide TSS total suspended solids

CL crude lipid CP crude protein

The efficiency for producing biofloc also needs to be elevated, if biofloc is used as a gradient of formulated feedstuff for replacement of fishmeal or soybean meal or used to feed to aquatic animals directly as a food with whole nutritional gradients usually contained in artificial feedstuff. The productivity of biofloc recent is not adequate for those uses in practical operations.

Moreover, the improvement of biofloc palatability should be researched, which is important to the utilization of biofloc either eaten in situ or used as a food source [76]. Attractants or feeding promoting agents, like garlicin, betaine (trimethylglycine), trimethylamine oxide (TMAO), and s,s-dimethyl-β-propionic acid thetine (DMPT), could be taken into consideration as additives during development of biofloc in situ or preparing process for biofloc pellets. Thus, the effects of those agents on biofloc attraction to fish and shrimp should be studied in detail, respectively.

#### **9. Conclusions**

Biofloc technology (BFT) supplies a novel solution for this issue without huge water exchange, even zero water exchange. In general, ammonia would be removed quickly within several hours in a BFT system. Moreover, because of the very high nutritional value for fish and shrimp, bioflocs, the by-product of BFT, could also be reused as a complemented food in situ or a gradient for feedstuff to replace expensive fishmeal, and biofloc also could be processed to formulate diet to feed fish and shrimp directly. However, some aspects with regard to the effective use of biofloc as a food source for fish and shrimp, such as high lipid content, productivity, and palatability, need to be further researched in detail.

#### **Acknowledgements**

This work is supported by the development funds of the Chinese central government to guide local science and technology (2017CT5013); the Sci-Tech program of Hunan province, China (2016NK2132); and the science and research program of the Education Department of Hunan province, China (16C1085, 18B394).

#### **Conflict of interest**

The author declares no conflict of interest.

#### **Notes/thanks/other declarations**

The author also thanks the support from Collaborative Innovation Center (Hunan) for Efficient and Health Production of Fisheries, Hunan Engineering Research Center of Aquatic Organism Resources and Environmental Ecology, Hunan Engineering Research Center of Aquatic Organism Resources and Environmental Ecology, and Academician Workstation (Fisheries) of Hunan Province.

*Novel Biofloc Technology (BFT) for Ammonia Assimilation and Reuse in Aquaculture In Situ DOI: http://dx.doi.org/10.5772/intechopen.88993*
