i

A Seminar paper on

Biofloc technology and its potentiality for higher production of fish in

Bangladesh

Course code: GFB 598

Term: summer’20

Submitted to

Course Instructors Major Professor

Dr. A. K. M. Aminul Islam

Professor, Dept. of Genetics and Plant

Breeding

Prof. Dr. Md. Mizanur Rahman

Professor, Dept. of Soil Science

Dr. Md. Sanaullah Biswas

Associate Professor, Dept. of Horticulture

Dr. Dinesh Chandra Shaha

Associate Professor, Dept. of Fisheries

Management

BSMRAU, Gazipur 1706

Dr. Zinia Rahman

Associate Professor,

Dept. of Genetics and Fish Breeding

BSMRAU, Gazipur 1706

Submitted By

Rabeya Chowdhury Shapla

Program- Ms

Reg. No- 15-05-3606

Dept. of Genetics and Fish Breeding

Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur

1706

ii

Biofloc technology and its potentiality for higher production of fish in Bangladesh1

By

Rabeya Chowdhury Shapla2

ABSTRACT

Biofloc technology (BFT), the new “blue revolution” in aquaculture, could be promising in

attaining it’s sustainability to aquaculture production without sacrificing the quality. It is mainly

based on the principle of waste nutrients recycling, in particular nitrogen, into microbial biomass

that can be used in situ by the cultured animals or be harvested and processed into feed

ingredients. A rearing of mono-sex GIFT tilapia attained a significantly (P<0.05) difference in

survival rate of fish among the treatments. Another study evaluates the biofloc technology (BFT)

in light-limited tank culture of Nile tilapia (Oreochromis niloticus). Two biofloc treatments and

one control were managed in indoor tanks: BFT fed a diet of 35% crude protein (CP), BFT fed a

diet of 24% CP, and clean water control without biofloc with 35% CP. BFT . Fish survival was

100%. Net fish production was 45% higher within the BFT tanks than within the control tanks

confirming the use of biofloc by fish as food. The study of evaluating the effect of biofloc

technology (BFT) application on water quality and production performance of tilapia

(Oreochromis sp.) at different stocking densities. The highest TAN and nitrite-nitrogen were

observed in control treatment at stocking density of 100 fish/m3 (3.97 mg TAN/L and 9.29 mg

NO2-N/L, respectively). The highest total yield was observed on top of things treatment at the

very best density treatment (43.50 kg). An experiment was conducted to research the expansion,

digestive activity of raising genetically improved farmed tilapia (GIFT) during a (RAS) and an

inside (BFT) system. At the top of the study, the individual fish weight at harvest was 22%

higher within the BFT fish than within the RAS fish.

Keywords: Biofloc, nutrients recycling, microbial biomass, TAN

1 A seminar paper for the course GFB598, Summer’ 20. 2 MS student, department of Genetics & Fish Breeding, BSMRAU, Gazipur 1706.

iii

LIST OF CONTENTS

Sl.

No.

Topic

Page no.

01 Abstract ii

02 List of contents iii

03 List of tables iv

04 List of figures v

05 CHAPTER 1: Introduction 1-2

06 CHAPTER 2: Materials and methods 4

07 CHAPTER 3: Review of Findings 5-21

08 CHAPTER 4: Conclusion 22

09 References 23-29

iv

LIST OF TABLES

Sl. No.

Name of the Tables

Page No.

01 Proximate composition of biofloc 06

02 Some of the study conducted in fish with reference

to (BFT) based culture Systems

07

03 Mean values (±SE) of water quality parameters

observed throughout the study period

09

04 Growth performance of Nile tilapia in activated

suspension and clean water tanks fed

different levels of protein feed

14

05 Growth performance and feed utilization of tilapia

in re-circulating aquaculture system and indoor

biofloc technology system.

15

06 Effect of BFT and BFT with 10% WE on growth

performance

16

07

Effect of five carbon: nitrogen ratios in the

performance of Nile tilapia Oreochromis niloticus

in a biofloc system for six months, in comparison

with a standard method of cultivation (control).

18

v

LIST OF FIGURES

Sl. No

Name of the Figures

Page No.

01 Overview of possible parameters of bioflocs

technology and their probable effects.

02

02 Components needed for biofloc preparation 05

03 Scheme of biofloc technology in pond 06

04 Nitrogen and total phosphate dynamics in the RAS

and BFT tanks. RAS: Recirculating Aquaculture

System; BFT: Biofloc Technology.

12

05 Effect of BFT and BFT with 10% WE on nitrate of

Nile tilapia, O. niloticus, fingerlings rearing tanks.

13

06

Effect of different biofloc starters on ammonia, nitrate,

and nitrite concentrations in the cultured tilapia O.

niloticus system.

19

07 Specific activities of protease and amylase in digestive

glands, stomachs and intestines of juvenile

Litopenaeus vannamei in the control and two bioflocs

treatments with two C/N ratios (15, 20) at the end of

30-day feeding experiment.

21

1

CHAPTER 1

INTRODUCTION

With almost seven billion people on world, the requirements for aquatic food which is increasing

accordingly and hence, expansion and intensification of aquaculture production are highly

required. Aquaculture as a food‐producing sector offers many opportunities to remove poverty,

hunger and malnutrition, generates economic growth and ensures better use of natural resources

(FAO, 2017)

Biofloc technology (BFT) offers benefits in improving aquaculture production that could

contribute to the achievement of sustainable development goals. This technology may result in

higher productivity with less impact to the environment. Biofloc technology is mainly based on

the principle of waste nutrients recycling, in particular nitrogen, into microbial biomass that can

be used in situ by the cultured animals or can be harvested and processed into feed ingredients

(Avnimelech, 2009; Kuhn et al., 2010). Heterotrophic microbiota is stimulated to grow by

steering the C/N ratio in the water through the modification of the carbohydrate content in the

feed or by the addition of an outer carbon source in the water (Avnimelech et al., 1999), so that

the bacteria can assimilate the waste ammonium for new biomass production. Hence,

ammonium/ammonia can be maintained at a low and non‐toxic concentration so that water

replacement is no longer required. Biofloc technology enhances the production and productivity

by its contribution to the supply of good quality fish juveniles, the latter being one of the most

important inputs in the production. In addition, it contributes to the improvement of the fish

production. In relation to the former, biofloc technology could support the supply of good quality

seeds by improving the reproductive performance of aquaculture animals and by enhancing the

larval immunity and robustness (Ekasari et al., 2015; Ekasari et al., 2016 and Emerenciano et al.,

2013)

This systems can also be developed and conduct in integration with other food production, by

advancing productive integrated systems, focusing at producing more food and also be feed

from the same area of land with less input. The biofloc technology is still in its developing

stage. More research is needed to optimize the system (in relation to operational parameters) e.g.

2

in relation to nutrient recycling. In addition, research findings will need to be shared with

farmers as the implementation of biofloc technology will require upgrading their skills.

Biofloc systems were also helped to prevent the introduction of disease to a farm from incoming

water. In the past, standard operation of shrimp ponds included water exchange (typically 10

percent per day) used as a method to control water quality. In estuarine areas with many shrimp

farms go through water exchange, disease would spread among farms. Reducing water exchange

is an obvious strategy for developing farm biosecurity. Shrimp farming moving toward more

closed and intensive production where waste treatment is more inter-analyzed. Some types of

biofloc systems have been used in commercial aquaculture or evaluated in research. The two

basic types are those that are exposed to natural light and those that are not exposed. One of this

systems exposed to natural light include outdoor, lined ponds or tanks and lined raceways for

shrimp culture in greenhouses. A complex mixture of algal and bacterial composition control

water quality in such “greenwater” biofloc systems. Maximum biofloc systems in commercial

use are greenwater. However, some biofloc systems (raceways and tanks) have been installed in

closed buildings with no contact to natural light. These systems are worked as “brown- water”

biofloc systems, where only bacterial processes control water quality.

Fig 1: Overview of possible parameters of bioflocs technology and their probable effects. (crab,

2010)

3

OBJECTIVES

The study has undertaken to accomplish the following objectives;

The general objective of this study was to explore the possible contribution of biofloc

technology application to aquaculture production, while maintaining sustainable

practices,

Aquaculture production can be optimized by, the maintenance of water quality by the

uptake of nitrogen compounds,

Providing an optimum nutrition to ensure maximum growth as well as increasing culture

feasibility by reducing feed conversion ratio and a decrease of feed costs.

4

CHAPTER 2

MATERIALS AND METHODS

This seminar paper is exclusively a review paper. All of the information has been collected from

the secondary sources. The study was carried out based on the information through review of

related thesis, journals, reports and books. The necessary data were collected from source like

internet, National Fish week compendiums, different annual statistical yearbooks of Bangladesh,

newspapers, watching with different on-going researches in YouTube. I got suggestion and

valuable information from my major professor and my course instructors. I myself compiled the

collected information and prepared this seminar paper.

5

CHAPTER 3

REVIEW OF FINDINGS

3.1. Basic view of biofloc

3.1.1 Essential component of Biofloc preparation

In general, biofloc is the macro-aggregation of bacteria, algae, detritus and other decomposed

components (Avnimelech et al., 1994). It is the combination of bacteria, diatoms, zooplankton,

protozoa, macro-algae, feces, uneaten feed (Fig. 2), and exoskeleton from dead organisms

(Decamp et al., 2008). It is a group of biotic and abiotic particulate components suspended in the

water which includes bacteria, planktons, and other organic materials (Hargreaves et al., 2006)

Fig 2: Components needed for biofloc preparation (Source: Daniel N and P. Nageswari 2017)

3.1.2. Nutritional quality of biofloc

The biofloc samples were analyzed for Kjeldahl nitrogen (Kj-N), total ammonia nitrogen (TAN),

total suspended solids (TSS) and volatile suspended solids (VSS). These properties were

determined following APHA (1998). The difference between Kjeldahl-N and TAN was used to

calculate the protein content of the bioflocs by multiplying the organic nitrogen content by 6.25

(Jauncey, 1982). The ash content was determined using TSS and VSS values. Lipids were

extracted according to Folch et al. (1957), using the modification of Ways and Hanahan (1964).

Protein, lipid and ash content were expressed as percentage of the dry weight (% DW) of the

bioflocs.

6

The total carbohydrate was calculated according to the following formula: carbohydrate (%

DW) = 100 – (crude protein (% DW) + lipid (% DW) + ash (% DW)) (Manush et al., 2005). The

gross energy content of the diets was calculated using kilo joule (kJ/g DW) values of 23.0, 38.1

and 17.2 for protein, lipid and carbohydrate respectively in (Table. 1) (Tacon, 1990).

Table. 1: Proximate composition of biofloc.

Component Crude amount

Protein 23.0 (kJ/g DW)

Lipid 38.1 (kJ/g DW)

Carbohydrate 17.2 (kJ/g DW)

3.1.3. Biofloc preparation

If nitrogen and carbon are well balanced in the solution, ammonium in addition to organic

nitrogenous waste will be converted into bacterial biomass (Schneider et al., 2005). By adding

carbohydrates to the pond, heterotrophic bacterial growth is stimulated and nitrogen uptake

through the production of microbial proteins takes place (Avnimelech et al., 1999) (Fig: 3). The

microbial biomass yield per unit substrate of heterotrophic bacteria is about 0.5 g biomass C/g

substrate C used (Eding et al., 2006) .Suspended growth in ponds consists of phytoplankton,

bacteria, aggregates of living and dead particulate organic matter, and grazers of the bacteria

(Hargreaves et al., 2006).

Fig 3: Scheme of biofloc technology in pond (Source; Google)

7

3.1.4. Benefits of Biofloc Technology (BFT) system

Eco-friendly culture system.

It reduces environmental impact.

Improves land and water use efficiency

Limited or zero water exchange

It enhances growth performance, survival rate, and feed conversion in the culture

systems.

Higher bio-security.

Reduces water pollution and the risk of introduction and spread of pathogens

Cost-effective feed production.

It lowered utilization of protein rich feed and cost of standard feed.

It decreases the pressure on capture fisheries i.e., use of cheaper food fish and trash fish

for fish feed formulation.

Table 2: Some of the study conducted in fish with reference to (BFT) based culture Systems

SL. No. Species studied Results acquired in the study with (BFT)

01 Labeo rohita Reduced the artificial feed reliance and improved

the utilization of bioflocs as feed to 50% (Sharma

et al., 2015)

02 Oreochromis niloticus Fish survival was 100% and results in biofloc

utilization as food (Azim and Little, et al., 2008)

03 Oreochromis sps. Improvement in the water quality, fish survival and

minimization in the external feed requirement

(Sharma et al., 2015)

04 Litopenaeus vannamei Promoted the animal growth, health, digestion and

feed utilization performances (Xu et al., 2012)

05 Penaeus monodon Gave the beneficial effects on growth performances

and digestive enzyme activities (Anand et al., 2013)

06 Litopenaeus vannamei Increase in 30% growth and survival of shrimp in

Biofloc treatment (Piedrahita, 2003)

8

3.2. Applications and results

3.2.1. Physico-chemical parameter of water in (BFT)

It is considered that most of the uneaten feeds that present in the water damage the pond water

and threaten the animals to disease susceptibility (Francis-Floyd et al., 2009). It was

demonstrated in the earlier findings that adopting biofloc technology would solve the problems

concerned with ammonia toxicity, with the increasing consumption of nitrogen by heterotrophic

bacteria the nitrification process advances, which ensures the reduction in the concentration of

ammonium in the culture systems (Hargreaves, 2006). The study also demonstrated that the

production rate for heterotrophic bacteria for the utilization of ammonium is 10 times greater by

heterotrophic bacteria as compared to that of nitrifying bacteria (Hargreaves, 2006)

A study was conducted by (Nahar and Bakar et al., 2015), where the values of water quality

parameters such as water temperature, dissolved oxygen, pH and transparency in different

treatments are shown in (Table. 3). The mean values of water temperature in different treatments

were 23.33±1.04, 23.21±1.06, 23.10±1.03 and 23.15±1.03°C in CF, WB, BFT and RWB,

respectively (Table 3). The highest (29.91°C) and lowest (17.86°C) water temperature in the

present study might be due to the bright sunshine and cold weather. The amount of dissolved

oxygen in the water is directly influenced by temperature and also affects the cultured species

metabolism, which determines fish growth aspects. In BFT set ups, an intermediate water

temperature of 20-25°C could be best to obtain stable flocs proposed by Craig and Helfrich.

Tilapia (O. niloticus) didn't grow at temperature below 16°C and didn't survive at temperature

below 10°C for quite a couple of days. In the present study, the day temperature within the ponds

didn't fall below 17.86°C and fish probably didn't stop eating. Dissolved Oxygen (DO) varied

from 4.25 to 6.10 mg/l with mean values of 5.18±0.17, 5.05±0.16, and 4.83±0.17 and 4.92±0.19

mg/l in CF, WB, BFT and RWB, respectively

9

Table.3. Mean values (±SE) of water quality parameters observed throughout the study period Water quality

parameters

CF WB BFT RWB

Temperature

(°C)

23.33±1.04 23.21±1.06 23.10±1.03 23.15±1.03

Dissolved

oxygen (mg/l)

5.18±0.17 5.05±0.16 4.83±0.17 4.92±0.19

pH 7.00±0.03 7.06±0.04 7.10±0.05 7.08±0.05

Transparency

(cm)

34.24±0.25 29.86±0.01 26.06±0.39 31.06±0.30

According to Luo et al., (2013) in the BFT tanks, the TAN (Total Ammonia Nitrogen) was

primarily from the decomposition of organic matter such as fish waste and dead microbes in the

reactors. The TAN (Total Ammonia Nitrogen) can be rapidly taken up and stored by the biofloc

microbes by adding organic carbon to stimulate the growth of heterotrophic bacteria. However,

the packaging of nitrogen in microbial cells is temporary because cells turn over rapidly and

release nitrogen as NH3 when they decompose. Therefore, the TAN (Total Ammonia Nitrogen)

was repeatedly cycled between the dissolved NH3 and the flocs solids, exhibiting an obvious

fluctuation (Fig. 4A). The peaks of the TAN and NO2−-N occurred on day 20 during the BFT

system start-up. The highest concentrations of TAN and NO2−-N were 60 ± 0.45 mg L−1 (Fig.

4A) and 119 ± 2.01 mg L−1 (Fig. 4B), respectively. With the acclimation of the system, the TAN

and NO2—N started to decrease. At the end of the study, there were no detectable NO2

−-N, and

the TAN was less than 10 mg L−1. No apparent accumulation of NO3−-N was observed in the

culture tanks during the entire experiment (Fig. 4C). The safe level of NH3 for larval tilapia

(Oreochromis niloticus) is 0.42 mg L−1 (Benli and Köksal, 2005). When the NH3 fraction from

the TAN at an overall average pH of 7.11 and average temperature of 22 ± 0.15 °C,

approximately 0.5% are accounted for because the safe TAN level for Nile tilapia is 84 mg L−1,

10

which is higher than the highest TAN in the current study. Therefore, it can be concluded

that our BFT system is NH3 and toxicity-free. NO2−-N is an intermediate during both

nitrification and denitrification (Chuang et al., 2007; Ruiz et al., 2003). The accumulation of

NO2−-N is common in intensive aquaculture (Wang et al., 2004), probably due to the free

NH3 inhibition during nitrification and denitrification (Shi et al., 2011). Based on a

recommendation from Wuertz et al., (2013), salt was added to the BFT tanks (1%, w/w−1) to

compensate for the stress fromNO2−-N to the tilapia in the current experiment. The NO2

−-N

concentration in the BFT tanks was much higher than that from other reports (Asaduzzaman

et al., 2009; Xu and Pan, 2012), which is probably because of the higher stocking density in

the current experiment. There is no accumulation of NO3−-Nin the BFT tanks perhaps

because the process of nitrification might be inhibited by the high C: N ratio, the NO3 −-N

was used by the heterotrophic bacteria (Luo et al., 2013), or denitrification occurred in the

system. Previous studies on phosphorus dynamics in freshwater aquaculture systems have

revealed that much of the phosphorus added with the feed is unutilized by the cultured fish

and that a relatively large fraction (80%–90%) is released into the fish culture systems

(Barak et al., 2003). A targeted method for phosphorus removal in the current RAS was not

developed; therefore, the accumulation of PO4 3 −-P in the RAS tanks was 45 ± 1.23 mg L−1

at the end of the experiment (Fig. 4 D), whereas the PO4 3−-P level in the BFT tanks was as

low as 4.01 ± 0.34 mg L−1, which was probably because the growth and reproduction of the

biofloc microorganisms assimilated the phosphorus that was not used by the fish.

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Fig 4: Nitrogen and total phosphate dynamics in the RAS and BFT tanks. RAS: Recirculating

Aquaculture System; BFT: Biofloc Technology. (Luo and Gao et al., 2013)

In Abduljabbar et al., (2015) analyzed and compared the changing of TAN concentrations was

fairly consistent over time among the investigated groups with tendency to decrease with BFT

treatments than the control group (Fig. 5). The TAN were controlled in BFT treatments or BFT

with 10% WE via carbon source (molasses) addition to stimulate the growth of heterotrophic

bacteria, TAN can be used and stored by the formation of BFT microbes (Avnimelech et al.,

1999; Ebeling et al., 2006), which may explain why the TAN concentration did not exhibit

significant differences between the clean water control group and the BFT treatments.

The nitrate (NO3-N) reached each beak after four weeks of treatments for all treatments and

decreased gradually over time (Fig. 5). The least nitrate level was observed with BFT with zero

WE. The accumulation of nitrate during the first weeks may have been caused by nitrification

processes, which are common in BFT systems (Azim and Little, 2008 and Zhao, et al., 2012).

The subsequent reduction of nitrate in the BFT treatments likely occurred due to immobilization

by heterotrophic bacteria, which inhibited the nitrification and de-nitrification process (Azim and

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Little et al., 2008). Also, Luo et al. (2014) reported that nitrate did not accumulated in the BFT

tanks perhaps because the process of nitrification might be inhibited by the high C:N ratio, and

used by the heterotrophic bacteria or de-nitrification occurred in the system.

Fig 5: Effect of BFT and BFT with 10% WE on nitrate of Nile tilapia, (O. niloticus), fingerlings

rearing tanks.

BFT: Biofloc technology; WE: Water exchange.

3.2.2. Growth performance and fish yield parameters

A study was carried out by Azim and Little et al., (2008) to evaluate growth and fish yield

parameters of Tilapia are given in (Table.4). Tilapia survival was 100% in all treatment and

control tanks. Individual fish weight at harvest was 9–10% higher in the BFT treatments than in

the control. The BFT treatments contributed 44–46% greater individual weight gain and net fish

production than those in the control confirming the utilization of biofloc by fish as food. Most of

the tilapias are known to utilize in situ produced food particles including suspended bacteria

(Beveridge et al., 1989). Avnimelech (2007) has also confirmed that, the biofloc uptake by

Mozambique tilapia using stable nitrogen isotope labeling technique. However, there was no

significant difference in fish growth/production between 35% and 24% CP fed tanks under the

BFT. The FCR value was significantly higher in the control than in the BFT treatments.

Little et al., (2008) reviewed that the final biomass levels of 10–28 kg fish m−3 achieved in

indoor and outdoor BFT systems throughout the year.

13

A study was carried out by Azim and Little et al., (2008) to evaluate growth and fish yield

parameters of Tilapia are given in (Table.4). Tilapia survival was 100% altogether treatment and

control tanks. Individual fish weight at harvest was 9–10% higher within the BFT treatments

than within the control. The BFT treatments contributed 44–46% greater individual weight gain

and net fish production than those in the control confirming the utilization of biofloc by fish as

food. Most of the tilapias are known to utilize in situ produced food particles including

suspended bacteria (Beveridge et al., 1989; Beveridge and Baird, 2000).

Avnimelech et al., (2007) has also confirmed that, the biofloc uptake by Mozambique tilapia

using stable nitrogen isotope labeling technique. However, there was no significant difference in

fish growth/production between 35% and 24% CP fed tanks under the BFT. The FCR value was

significantly higher in the control than in the BFT treatments. Although there was clear evidence

that the biofloc significantly contributed to the expansion and production of fish. Little et al.,

(2008) reviewed that the final biomass levels of 10–28 kg fish m−3 achieved in indoor and

outdoor BFT systems throughout the year.

Table. 4 Growth performance of Nile tilapia in activated suspension and clean water tanks fed

with different levels of protein feed

Parameters 35% CP without

biofloc

35% CP with

biofloc

24% CP with

biofloc

Initial individual

weight (g)

99.61±13.74 100.69±13.61 98.45±12.71

Final individual weight

(g)

127.51±28.17 140.72±27.26 138.58±24.99

Survival (%) 100 100 100

Individual weight gain

(g)

27.9±0.69 40.04±3.04 40.08±4.34

Net yield (kg m−3) 3.35±0.08b 4.80±0.60 4.90±0.59

FCR 4.97±0.12 3.51±0.44 3.44±0.45

14

In the study of Luo and Gao ( 2013), Growth performance and feed utilization of fish and fish

yield parameters are described in (Table.5). Even when the water quality was not stable and there

were high fluctuations in the concentrations of TAN and NO2−-N, no fish died during the entire

experiment, and the fish in the BFT tanks grew more satisfactorily than those in the RAS tanks

did. The individual fish weight at harvest was 22% higher within the BFT fish than within the

RAS fish. The total weight gain and SGR of the BFT fish were, respectively, 129% and 12%

above those of the RAS fish. The FCR value in BFT treatment fish was 1.20 ± 0.03, 18% better

than that of the RAS fish, which had an FCR of 1.47 ± 0.02.

Table.5. Growth performance and feed utilization of tilapia in recirculating aquaculture system

and indoor biofloc technology system.

Parameters RAS BFT

Initial number (fish tank−1) 100 100

Initial mean weight (g

fish−1)

24.17 ± 2.49 24.17 ± 2.49

Final mean weight (g fish−1) 138.29 ± 34.61 168.58 ± 40.64

Survival rate (%) 100% 100%

Specific growth rate (%

day−1)

1.90 ± 0.30 2.13 ± 0.29

Weight gain (%) 472.14 ± 143.18 597.48 ± 168.16

Total weight gain (kg m−3) 28.87 36.95

15

A treatment was run by Abduljabbar et al., (2015) for the comparison in growth performance of

fishes between BFT treatments and BFT with 10% WE. The growth performance of fish in BFT

treatments and BFT with 10% WE was found higher significantly (P <0.05) than fish in the

control group in the case of (final body weight, weight gain, average daily gain and specific

growth rate). The increase of final weight was 28.70 and 22.20% with BFT or BFT with 10%

WE, respectively, than in the control group. Survival rate was found high (98-99%) with all

conducted treatments, where rearing fish under BFT technology with zero WE or limited (10%)

WE did not negatively affect the survival rate (Table.6). Moreover, the present results verified

that intensive tilapia production in the BFT systems increase feed and nutrients utilization

significantly (P <0.05) compared with in the control.

According to Krummenauer et al., (2008) shrimp reared in the environment with molasses

addition exhibited a survival rate, final weight and specific growth rate (SGR) significantly

higher than those of the control did.

Table.6. Effect of BFT and BFT with 10% WE on growth performance

Item Control BFT BFT + 10% WE

Initial weight (g/fish) 3.38±0.02 3.44±0.02 3.37±0.03

Feed intake (g/fish 20.16b±0.15 22.67a±0.23 22.19a±0.24

Weight gain (g/fish) 8.78b±0.26 12.22a±0.38 11.49a±0.27

Final weight (g/fish) 12.16b±0.25 15.65a±0.36 14.86a±0.28

ADG (g/fish/day) 0.07b±0.0 0.10a±0.0 0.10a±0.0

SGR (%/day) 1.07b±0.02 1.26a±0.02 1.24a±0.01

Survival rate (%) 98±0.82 99±0.67 98±1.11

*Means followed by different letters in the same raw differ significantly (P.0.05).

BFT: Biofloc technology; WE: Water exchange; ADG: Average daily gain; SGR: Specific

growth rate; FCR: Feed conversion ratio; PER: Protein efficiency ratio; PPV: Protein productive

value.

16

3.2.3. Maintaining C/N ratio

The maintenance of C/N ratio is quite prerequisite for controlling of accumulating organic

nitrogen and for the production of microbial communities in the water (Asaduzzaman et al., 2008

and Emerenciano et al., 2012). The inorganic nitrogen is converted into organic nitrogen when

C: N ratio is sufficient to produce bacterial cells (Aly et al., 2008). As carbohydrate is involved

in the part of respiration process, during aerobic situations the condition of C: N ratio must be

more than bacterial body compositions (Emerenciano et al., 2013). It was found that around 10

mg NH4+-N/L can be completely absorbed when glucose was added as a substrate and when the

maintenance of C/N ratio was 10:1. To minimize the synthetic feed requirement, the practice of

accelerating C: N of upper than 10:1 by utilizing different low-cost carbon sources which are

locally obtainable is common in biofloc waters (Crab et al., 2010). Apart from reducing the feed

cost, utilization of biofloc components will also decrease the amount of protein in the feed

(Avnimelech, 1999; Hargreaves, 2006). It was established that the buildup of toxic inorganic

components including, NH4+ and NO2- are going to be stopped within the water when the

upkeep of C/N ratio is high in the biofloc system because the ammonium consumption by the

microbial community.

By Jorge et al., (2015), survival of juvenile tilapia in the biofloc treatments was similar and

significantly higher (94.60 ± 2.03%) than survival in the control (84.96 ± 1.53%) (Table.7)

During the first three months, exponential growth occurred in all tilapia. From months 4–6,

tilapia raised in the control had a significantly higher growth rate than tilapia in the biofloc

treatments. The high final weight of tilapia in the control treatment was a response to lower

density caused by higher early mortality (r = 0.81 and P b 0.001). The highest final weight,

weight gain, weight gain per day, and final biomass was in the 10:1 and 15:1 C: N treatments,

with no significant differences with tilapia in treatment 12.5:1. The lowest final weight and

weight gain occurred in the 17.5:1 and 20:1 C: N treatments. The feed conversion ratio in all

tilapia in the biofloc treatments was close to 1.06 ± 0.05, with consumption of feed of 1.60%

each day in all treatments and the control. Ranking of filet yield of the treatments was: 10:1 N

15:1 N control N 12.5:1 N 17.5:1 N 20: 1 (Table 7).

17

Table.7. Effect of five carbon: nitrogen ratios in the performance of Nile tilapia O. niloticus in a

biofloc system for six months, in comparison with a standard method of cultivation (control).

Variable Control 10:1 15:1 17.5:1 20:1

S (%) 84.96 ± 1.53 94.75 ± 1.53 94.28 ± 2.08 94.18 ± 1.53 94.32 ±

1.53

IW (g) 38.4 ± 1.49 38.4 ± 1.49 38.4 ± 1.49 38.4 ± 1.49 38.4 ± 1.49

FW (g) 280.89 ±

5.43

254.31 ± 20.50 251.56 ± 15.76 233.31 ±

10.87

230.66 ±

10.38

IGW (g) 223.69 ±

21.03

196.26 ± 29.54 193.52 ± 23.91 176.12 ±

22.44

172.62 ±

19.88

WGD

(g/d)

1.24 ± 0.11 1.09 ± 0.16 1.07 ± 0.13 0.97 ± 0.12 0.95 ± 0.11

FCR 1.02 ± 0.01 1.01 ± 0.01 1.03 ± 0.01 1.13 ± 0.01 1.14 ± 0.01

FB

(kg/m3 )

17.86 ± 0.16 18.03 ± 0.25 17.73 ± 0.18 16.44 ± 0.04 16.28 ±

0.02

FP (%) 29.53 ± 1.50 32.24 ± 1.83 31.62 ± 1.84 27.21 ± 1.10 26.77 ±

1.95

Different letters in the same row represent significant differences at P b 0.05. FW = final weight,

FL = final length, IGW = individually gain weight, WGD = weight gained per day, FCR = feed

conversion rate, FB = final biomass, FP = filet production.

18

The study by Putra I. et al., (2010), revealed that the concentrations of ammonia, nitrite, and

nitrate were significantly lower within the biofloc system using starters compared with those

within the system without a starter (control). Biofloc has probiotic bacteria which will change

ammonia to nontoxic materials (such as nitrate) that are useful for phytoplankton growth.

Therefore, the ammonia and nitrate concentrations are low in the culture media (Hargreaves et

al., 2005). Biofloc doesn't necessarily only contain bacteria (for example, Bacillus), but is

additionally composed of other useful microorganisms like microalgae and zooplankton that are

trapped by organic particles (Crab, 2007). Algae and zooplankton can be used by cultured biota

(tilapia) as natural food.

Fig 6: Effect of different biofloc starters on ammonia, nitrate, and nitrite concentrations in the

cultured tilapia system

(a) Concentrations of ammonia, (b) nitrate, and (c) nitrate during 40 days of the experiment. A =

control treatment, B = molasses starter, C = tapioca starter, and D = sucrose starter.

19

In general, the starters used in this study were carbohydrate compounds. However, the study

showed that the molasses starter yielded slightly better results compared with the other starters.

This finding indicated that molasses was the best carbon source for biofloc in the tilapia culture

system. Molasses can provide a sufficient carbon level for heterotrophic bacteria that use this

carbon as an energy source for growth (Avnimelech et al., 2009). Molasses are a liquid

byproduct from the sugar industry. This material features a total carbon content of around 37%.

Therefore, molasses are rapidly soluble in water and can be quickly absorbed by heterotrophic

bacteria. In terms of chemical structure, molasses are classified as an easy carbohydrate

containing six C atoms (monosaccharides), while sucrose (treatment D) may be a combination of

two monosaccharides that contains 12 C atoms (sucrose). Tapioca is classified as a complex

carbohydrate (60,000 C atoms) and is more slowly digested by bacteria than molasses (Azhar,

2013).

3.2.4. Digestive enzyme activity during biofloc culture system

In the current study of Xu and Qing Pan et al., (2012), protease and amylase activities of the

shrimp in three groups were tissues-specific. Both enzymes activities were found highest in the

digestive gland, intermediate in the stomach, and lowest in the intestine. Although not

statistically significant, enhanced protease and amylase activities in the digestive glands of the

shrimp were observed in both biofloc treatments (Fig. 6A–B). Protease and amylase activities in

the stomachs of the shrimp in both biofloc treatments were significantly higher than those in the

control (Fig. 6C–D); while a decreasing trend of protease and amylase activities in the intestines

of the shrimp in both biofloc treatments was observed (Fig. 6E–F). A general enhancement in

protease and amylase activities of the shrimp in both biofloc treatments was observed, though the

effect of the bioflocs on each enzyme activity performed inconsistently among different digestive

tissues: digestive gland, stomach and intestine.

20

Fig 7: Specific activities of protease and amylase in digestive glands, stomachs and intestines of

juvenile L. vannamei in the control and two bioflocs treatments with two C/N ratios (15, 20) at

the end of 30-day feeding experiment. Means±S.E. indicated. n=4. Means within the same tissue

with different letters are significantly different (Pb0.05).

21

3.3. Potentiality of Biofloc technology (BFT)

This technology is essentially of zero water exchange oriented i.e. water exchange isn't required

within the culture ponds; therefore it required less water input which isn't only economical to the

farmers, but these also will minimize the pathogenic entry of animals through water and certify

for more biosecurity within the fish culture.

It also promises the less environmental impacts and footprints (Wasielesky et al., 2006).This

technology allows the animals to rear under the upper stocking density with effective feed

management (Crab et al., 2010; Crab et al., 2012).

The requirement for the feed is considerably less, as biofloc itself will be a feed for the cultivable

animals, which results in the lower FCR (Aiyushirota , 2009; Krummenauer, 2011; Perez-

Fuentes et al., 2013). Therefore, application of the technology will reduce the feed cost to the

farmers.

Biofloc increases the survival of fish since the beneficial microorganisms dominate in the biofloc

acts as an antagonism to the pathogenic bacteria which prevent the disease outbreak and expand

the percentage of survival during the harvest. This way (beneficial) bacteria present in the

biofloc prevent the colonization of any harmful bacteria that ensure the highest survival rate of

the fish in the farms (Megahed, 2010; Samocha, 2007; Perez-Fuentes et al., 2013).

Biofloc bacteria produce the poly hydroxyl butyrate (PHB) which is beneficial in the digestion

and metabolism of fatty acid and growth increment to the fish (De. Schryver et al., 2012).

Biofloc waters rich within the heterotrophic bacteria which utilize the toxic nitrogenous matters

as a substrate for his or her growth that helps maintaining the water quality through reducing the

organic loads as well as biochemical oxygen demand of the system (Avnimelech, 1994; Burford

et al., 2004).

Bioflocs comprise a wide assemblage of bacteria, algae, protozoa and other zooplankton

organisms, perhaps as many as 1000-2000 different species. As yet we do not know enough

about the composition of the bioflocs, nor our ability to affect it and the different effects it may

have on fish production and on the eco-stability of the system. It has been shown that the

immune systems of shrimp are enhanced in the presence of bioflocs and there is a lower

incidence of diseases among shrimp grown in biofloc systems.

22

It has demonstrated the probiotic effects of bioflocs against Streptococcus infection in tilapia.

Research on the effects of bioflocs on diseases is actively ongoing, and we can expect getting

more on how to use this system to control diseases.

Interesting new results demonstrate the effects of bioflocs on the fecundity of both shrimp and

tilapia: in both cases the number of eggs per female was about doubled. We do not know exactly

the mechanism of this effect. It is possibly caused by the top quality of the biofloc feed

components, better water quality, or the presence of hormones (or of components having

hormonal effects).

Biofloc technology has become a common way of running hatcheries and nurseries. Moreover,

biofloc systems are environmentally friendly due to the fact that there is almost no release of

nutrient rich drainage water to the environment.

23

CHAPTER 4

CONCLUSION

Biofloc technology offers benefits in improving aquaculture production that would contribute to

the achievement of sustainable development goals. This technology could result in higher

production capacity with less impact to the environment. Furthermore, biofloc systems are often

developed and performed in integrated production with other food, thus enhancing productive

integrated systems, with the aim of manufacturing more food and feed from the same area of

land with fewer input. The biofloc technology remains in its infant stage. A lot more research is

needed to optimize the system; in relation to operational parameters e.g. in relation to nutrient

recycling, production and immunological effects. In addition, research findings will get to be

communicated to farmers because the implementation of biofloc technology would require

upgrading their skills. This review paper has showed the growth, digestive activity, welfare, and

water quality parameters of raising GIFT in RAS tanks and BFT tanks. At the beginning of the

study, the Initial mean weight (g fish−1) 24.17 ± 2.49 in RAS and 24.10 ± 2.44 for BFT treatment,

but at the end of the experiment, Final mean weight (g fish−1) was found 138.29 ± 34.61 in RAS

tanks and 168.58 ± 40.64 in the BFT tanks. The fishes flourished in both environments; however,

the BFT fish were superior to the RAS fish, and no mortality was found among the BFT fish,

although the accumulation of NO2−-N and TAN was observed in the tanks. The crude protein

content within the biofloc met the nutritional requirements of tilapia, but the crude lipid

concentration was quite low. A significant difference was found for lipase in the intestines and

stomachs of the fish cultured using both models; however, no substantial difference was found

for protease.

Various kinds of beneficial features can be ascribed to biofloc technology, from water quality

control to in situ feed production and some possible extra features. Biofloc technology offers

aquaculture a sustainable tool to simultaneous in its environmental, social and economical issues

concurrent with its growth. Researchers are challenged to further develop this technique and

farmers to implement it in their future aquaculture systems. The basics of the technology is there,

but its further development, fine-tuning and implementation will need further research and

development from the present and future generation of researchers, farmers and consumers to

form this system a keystone of future sustainable aquaculture.

24

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