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Biofloc Technology – A Practical Guide Book

  • January 2012
  • Edition: 2
  • Publisher: The World Aquaculture society
  • Editor: Avnimelech, Y.
Authors:
Yoram Avnimelech at Technion - Israel Institute of Technology
Yoram Avnimelech
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19
World AquAculture
Reprinted from World Aquaculture 34(4):19-21. ©2003 World Aquaculture Society
Control of microbial activity
in aquaculture systems: active
suspension ponds
Yoram avnimelech1
The control of aquaculture systems
through the manipulation of microbial
activity became an important and com-
monly discussed technology arising from
the development of intensive aquaculture.
Aquaculture depended, traditionally, on
algal activity. Growing sh, including
crustaceans or other cultured aquatic
animals in water bodies depends, in tra-
ditional aquaculture, on algae generating
the base for the food chain or food web,
to feed the sh. Basic properties related to
algae control are listed in Table 1. Algal
productivity in non-fed ponds depends on
the level of inorganic nutrients, mostly
phosphorus (P) and nitrogen (N). Thus,
one of the rst stages of intensication
was to add inorganic fertilizers to the
pond. Following the elimination of nutri-
ents las a limiting factor, as is common in
well fertilized or fed ponds, productivity
becomes limited by solar radiation reach-
ing the algae. With optimal solar radiation
Table 1. Comparison of algae and bacterial controlled systems.
Property Algae Control Bacteria Control
Energy source Solar radiation Primarily organic matter
Occurrence Ponds with low organic matter Dominance in ponds with high supply and
concentration. Algae density increases concentration of organic substrate, normally
with the availability of nutrients up to limited to intensive ponds with zero to low
limitation of light. water exchange.
Sensitivity to Light is essential (activity is decreased Does not need light. Adapts to a variety of
environmental variables on cloudy days). Crashes are common. conditions. Crashes are exceptional.
Effect on oxygen Oxygen is produced during the day and Oxygen is consumed.
consumed at night.
Relevant activities Primary production: produces organic Degradation of organic matter. Nitrication.
matter and oxygen. Ammonia uptake. Production of microbial protein.
Inorganic nitrogen control Uptake driven by primary production Uptake of nitrogen affected by the C:N ratio
Maximum Capacity ca. 0.7 g NH+/m2/ in organic matter. Practically unlimited
day. capacity.
Potential capacity Normally, daily primary production Limited by substrate concentration
does not exceed 4 g O2/m2. and rate constant of degradation.
and algal activity, primary productivity
(PP) can reach a maximal daily level of 8-
10 g carbon (C) per m2 (Boyd and Tucker
1998). However, normal high values are
in the range of about 4 g C/m2 day (Wetzel
1975). The assimilated organic carbon
is the base of the food web. Only part
of it may be consumed directly by sh,
inasmuch as there is no control over the
species of algae that grow in the pond.
Algae supply other services to the
pond. A product associated with carbon
assimilation is the production of oxygen:6
CO2 + 6 H2O -- C6H12O6 + 6O2 ( 1 )
Primary production of 4 g C/m2 day
adds 10.7 g/m2 of oxygen; yet, only a
fraction of that is a net addition to the
pond. In the long run, all the organic
carbon is respired and all of the oxygen
that is produced is then consumed. The
benet to the pond stems from the fact that
part of the organic matter settles as dead
algae or other particulate organic matter,
and its microbial degradation takes place
only later. This is the reason for oxygen
problems in old ponds, where the sedi-
ment oxygen consumption becomes an
important fraction of the pond oxygen
balance. This is also the reason for the
recommended drying of the pond bottom
to oxidize the organic matter by exposing
it to the air. An additional reason leading
to inefcient use of the produced oxygen
by algae is that oxygen is produced mostly
in the top water layer, leading to oxygen
supersaturation in that layer and to its
release to the atmosphere.
One of the problems associated with
the intensication of pond aquaculture
is the accumulation of ammonia in the
water. This accumulation places the sh
at risk from elevated levels of the toxic
ammonia (NH3) and nitrite (NO2
-) spe-
cies. Algae help to alleviate this problem
because they take up nitrogen from the
20 December 2003
depends on an ample supply of oxygen, though
their sensitivity toward low oxygen is far be-
low that of sh. The number of bacteria in
zero exchange intensive ponds was found to
be in the order of 107-108 cells/ml (McIntosh
2000). The level of organic matter in ponds
tends to reach a steady state as a result of
a balance between the addition of organic
matter and its microbial degradation.
Continual aeration is conducive to the
development of nitrifying bacteria that
oxidize the excreted ammonia, rst to
nitrite and then to nitrate (NO3
-). Nitrate
is not toxic to sh at the levels found
in ponds and it serves as an oxidizing agent, preventing the
development of anaerobic conditions which can lead to several
fermentation processes and to the build up of toxic reduced
compounds. Nitrifying bacterial development is rather slow. It
may take 2-3 weeks from the day the pond is lled until the full
oxidation of ammonia to nitrate, with a possible short period of
nitrite accumulation when the rst stage of ammonia oxidation
has developed while the second is still evolving (Avnimelech
et al. 1986).
Though intensive nitrication is a very efcient mechanism
to reduce the accumulation of ammonia and nitrite, microbial
control enables a better and more efcient methods of reducing
toxic nitrogen metabolites. Bacterial cells are made primarily of
proteins. The carbon:nitrogen ratio of most microbes is about 4:5.
When bacteria are fed organic substrates that contain mostly carbon
(starch, molasses, cassava meal), they must take up nitrogen from
the water to produce the protein needed for cell growth and multi-
plication. Thus, the addition of carbonaceous materials leads to the
conversion of inorganic deleterious nitrogen to microbial proteins.
Roughly, 20-25 g of carbonaceous material are needed
to convert 1 g of ammonia nitrogen into
microbial protein (Avnimelech 1999).
This process is relatively fast and it is
possible to reduce an elevated level of
ammonia to any desired level within a
period of 1-3 days. One feature of this
mechanism is the possibility of using
the microbial protein as a source of
protein for sh.
The availability of microbial pro-
tein is not trivial nor is harvesting. Individual bacteria
are too small to be harvested physically by sh. In addition, the
digestibility of the bacterial protein must be determined. In a
series of tank and commercial size pond experiments it was found
that tilapia ingest and digest the microbial protein (Avnimelech
et al. 1989). Similar results were found with shrimp (McIntosh
2000) and bass (Milstein et al. 2001). The harvesting of the bac-
teria were possible because in dense microbial suspensions the
organisms tend to form ocs that were visible, having a size of a
few tenths of a millimeter. These ocs can be directly harvested
or ltered. MacKintosh (2001) reported that in the Belize zero
exchange shrimp ponds occulation was enhanced through the
re-use of water from ponds that had a good occulation, seem-
ingly by selection of bacteria with high occulation potential.
water as a part of their metabolism. As shown in
equation (1), the basic activity of the algae leads
to the production of glucose. However, a
basic component of algal cells is a
protein that is synthesized from
glucose using nitrogen that is
adsorbed from the water. Ni-
trogen constitutes about 1/6
of the carbon in algal cells
(Wetzel 1975), thus the am-
monia uptake potential of a pond
with PP of 4 g C/m2 day, is 0.66 g of
ammonia nitrogen per day. A pond
carrying 10 tons of sh/ha and fed
with 40 percent protein feed at a
rate of 2 percent bodyweight, gets
1.24 g N/m2 day, and roughly 75
percent of it, or 0.93 g N/m2, is released into the water. Thus, the
algae that can serve as a good buffer against ammonia toxicity
cannot function when pond intensication rises. Moreover, algal
control suffers from inherent instability. One factor is the strict
demand for light. A series of cloudy days, very common in the
tropics, leads to severe light limitations and to drastic reduction
of primary productivity. Oxygen concentration can be drastically
reduced and ammonia concentration increased following a series
of cloudy days.
To raise yields and to get better control of oxygen in ponds,
sh farmers introduce aerators into the pond system. Aerators
provide oxygen and, at the same time, mix the water. Intensive
aeration provides optimal conditions for aerobic bacteria and is
a feature typically found in bio-techno-
logical microbial-based industries. An
additional factor leading to the micro-
bial dominance in intensive ponds is
the limitation on water exchange.
Water exchange is one of the few controls
in algae dominated systems. When the water contains a
surplus of algae, or a surplus of organic materials, oxygen
consumption exceeds supply. One means of overcoming
this is to exchange the organic rich water with cleaner water.
However, this practice is limited because of environmental
concerns and regulations, the risk of disease infestation result-
ing from the un-controlled introduction of water and, in part,
the expense of pumping. When water exchange is limited, as in
the case of zero exchange or minimal exchange regimes, organic
matter builds up in the water. Organic matter is the substrate
needed for the development of a heterotrophic microbial com-
munity, microbes that get their energy by metabolizing organic
molecules. Intensication, aeration, mixing and limited water
exchange lead to the development of microbial dominance in
the pond. In intensive sh culture systems using heterotrophic
microbial control, active suspension ponds (ASP) were studied
and implemented in the last two decades (Avnimelech et al
1992, Avnimelech et al. 1994, McIntosh 2000, Chamberlain et
al 2001).
Typical features of microbial dominant systems are presented
in Table 1. The size of the microbial population depends on the
supply of organic matter and the stability of the aerobic community
21
World AquAculture
References
Avnimelech Y. 1999. Carbon/nitrogen ratio as a control element in
aquaculture systems. Aquaculture 176:227-235
Avnimelech, Y., B. Weber, B. Hepher, A. Milstein and M. Zorn. 1986.
Studies in circulated sh ponds: Organic matter recycling and
nitrogen transformation. Aquaculture and Fisheries Management
17: 231-242.
Avnimelech, Y., S. Mokady and G.L. Schroeder. 1989. Circulated ponds
as efcient bioreactors for single-cell protein production. Bamidgeh
41:58-66.
Avnimelech, Y., S. Diab and M. Kochva. 1992. Control and utilization
of inorganic nitrogen in intensive sh culture ponds. Aquaculture
and Fisheries Management 23:421-430.
Avnimelech Y., M. Kochva and S. Diab. 1994. Development of controlled
intensive aquaculture systems with a limited water exchange and
adjusted carbon to nitrogen ratio. Bamidgeh 46:119-131
Avnimelech, Y.. and G. Ritvo. 2001. Aeration, Mixing and Sludge
Control in Shrimp Ponds. Global Aquaculture Advocate 4:51-53.
Boyd, C.E. and C.S. Tucker. 1998. Pond aquaculture water quality
ma nag eme nt. Kl uwe r Aca d emi c Pub lic ati ons . Dord rec ht,
Netherlands.
Chamberlain, G., Y. Avnimelech, R.P. McIntosh and M. Velasco. 2001.
Advantages of Aerated Microbial Reuse Systems with Balanced
C:N I: Nutrient transformation and water quality benets. Global
Aquaculture Alliance Advocate 4: 53-56.
McIntosh R.P. 2000. Changing paradigms in shrimp farming: V.
establishment of heterotrophic bacterial communities. Global
Aquaculture Alliance Advocate 3:52-54.
McIntosh R.P. 2001. Changing paradigms in shrimp farming: V.
establishment of heterotrophic bacterial communities. Global
Aquaculture Alliance Advocate 4:53-58.
Milstein, A., Y. Avnimelech, M. Zoran and D. Joseph. 2001. Growth
performance of hybrid bass and hybrid tilapia in conventional and
active suspension ponds. Bamidgeh 53:147-157.
Wetzel, R. G. 1975. Limnology. W.B. Saunders Co, Philadelphia,
Pennsylvania USA.
Table 2. Effect of added carbon substrate (wheat
our) on yield, feed conversion ratio, protein
conversion ratio (protein in feed/protein gain
in sh) and feed cost in intensive tilapia
ponds. Averages based on three replicates
in commercial scale ponds. (Adapted from
Avnimelech et al. 1994.)
Protein level in feed 30 percent 20
percent
Experiment 1 (51 days)
Feed C:N ratio 11.1 16.6
Daily gain (% body weight) 1.59 2.0
Food conversion ratio 2.62 2.17
Protein conversion ratio 4.38 2.42
Feed cost (US$/kg sh) 0.85 0.58
Experiment 2 (30 days)
Feed C:N ratio 16.6 11.1
Daily gain (% body weight) 1.63 2.22
Food conversion ratio 2.62 2.02
Protein conversion ratio 4.35 2.18
Fish or shrimp utilize
only about 25 per-
cent of the protein
in the feed. High
protein diets are
needed to com-
pe nsa te for the
low utilization
rate. This may be
a dominant factor
in feed expense,
inasmuch as pro-
tein is the most expensive fraction
of the feed. In addition there are global
uctuations in the quantities of animal protein
sources available that can be problematic. The utilization of protein
in active suspension ponds is doubled. The sh eat and digest the
feed-originated protein and use it again by ingesting and digesting
the microbial protein, actually a recycling of the non-utilized feed
protein. A demonstration of this effect, obtained in a eld trial, is
presented in Table 2. Very similar results were obtained in com-
mercial shrimp ponds (McIntosh 2000). The higher utilization of
feed leads to signicantly lower feed costs (Table 2).
Preliminary results indicate that microbial dominance may
help induce disease resistance in sh. Several observations as
well as a controlled experiment (Avnimelech and Ritvo 2001)
indicated that a dense heterotrophic population can act as an
antagonist against pathogens. This effect, a probiotic control
mechanism, deserves further study.
Conclusions
Microbial controlled ponds, (ASP), provide a stable control
over processes in the pond. The microbial control is stable, does
not depend on light intensity and is not sensitive to population
crashes. Microbial control leads to efcient degradation of waste
materials, efcient nitrication and, through the manipulation of
the C:N ratio, facilitates the control and recycling of nitrogen
and doubles the protein utilization.
The basic demands to establish and maintain microbial
dominance are:
a. The pond gas must be well aerated and mixed.
b. Concentration of organic substrates has to be high to support
the heterotrophic population. This is achieved in intensive
systems with zero or restricted water exchange. An addition
of organic substrates in the beginning of the culture cycle
may help promote the development of the microbial com-
munity.
c. Microbial controlled ponds rely on the development of natural
microbial populations. Presently, there is no microbial inocu-
lum proven to be effective in promoting the development of
microbial controlled ponds.
d. The efciency of microbial controlled ponds must be evalu-
ated for the given organism to be cultured.
Notes
1Dept of Agricultural Engineering, Technion, Israel Inst. of Technology,
Haifa, 32000, Israel agyoram@tx.technion.ac.il
... Aquaculture with zero or minimal water exchange can be successfully achieved with biofloc technology (BFT) (Ha. [3][4][5] This technology will reduce the frequency of discharge of wastewater nutrients into the environment, and will also reduce the likelihood of escape, as well as the prevalence of disease, [6,7] minimizing waste as well as recycling waste into feed, [8][9][10] creates environmentally friendly and sustainable fish farming, [11] and reduces the need to supply water [12] which is currently a problem for C. batrachus farming in urban areas. ...
... [26][27][28][29] Aquatic performance depends on many factors in the biofloc system. Biofloc production is influenced by many biological factors including stocking density, (2) First, the carbonated rice husks are mixed with cow dung in a ratio of 3 : 1, then moistened to 60%; (3) Lactic Acid Bacteria (LAB) which is a fermented product of rice washing and fresh cow's milk is added to the mixture and fermented for 20 days in an airtight bucket; (4) The carbonation product is put into a streaming cloth and hung in the fish pond as fertilizer. Carbon provides energy for LAB which breaks down excess feed and inorganic matter (waste) at the bottom of the pond and converts the waste into fish feed. ...
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Biofloc-based Catfish (Clarias batrachus) farming allows for improving water quality, and growth. To further optimize the biofloc technology, we modified it with carbonation and bio balls to improve the C/N ratio and the performance of the floc-forming bacterial consortium. The purpose of this study is to analyze several parameters such as floc volume, BOD (biological oxygen demand), COD(chemical oxygen demand), BOD/COD, TOM (total organic matter), TDS(total dissolved suspended), orthophosphate, sulfate. SGR(specific growth rate), FE(feed efficiency), FCR(feed conversion ratio), SR (survival rate) and to obtain appropriate and environmentally friendly technology that can be applied in producing Catfish based on biofloc. In this study, a completely randomized design was used with 5 treatments and 4 replications, From the results of the study obtained: floc volume (76–88 mL L⁻¹), BOD (2.152–2.367 mg L⁻¹), COD (5.462–7.312 mg L⁻¹), BOD/COD (0.324–0.394), TOM (5.1–19.2 mg L⁻¹), TDS (318–1560 mg L⁻¹), orthophosphate (0.7–9.1 mg L⁻¹), sulfate (18.1–34.0 mg L⁻¹), SGR (0.058–0.066), FE (90.89–98.79%), FCR (0.933–1.104), SR (84–88%). In the future, the application of a combination of carbonation and bio balls in Catfish farming based on biofloc is feasible to be developed.
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Article
  • Dec 2022
Budidaya ikan nila secara intensif dengan kepadatan tinggi menyebabkan tingginya limbah sehingga dapat berdampak pada rendahnya kualitas air. Hal ini juga akan memudahkan ikan terserang penyakit. Permasalahan lain pada budidaya ikan nila seperti tingginya penggunaan pakan. Permasalahan tersebur menyebabkan rendahnya produktivitas hasil budidaya ikan nila. Salah satu solusinya adalah dengan budidaya ikan nila sistem bioflok. Budidaya ikan nila menggunakan sistem bioflok telah terbukti mampu meningkatkan pertumbuhan ikan, meningkatkan kualitas air, flok yang terbentuk dapat dimanfaatkan sebagai sumber pakan sehingga mengurangi penggunaan pakan buatan. Tujuan dari kegiatan pengabdian masyarakat ini adalah memberikan wawasan terkait b budidaya ikan nila dengan menggunakan teknologi bioflok dan pelatihan cara pembuatan bioflok kepada pembudidaya ikan nila pada kelompok budidaya ikan yang ada di Danau Ngade. Kegiatan dilakukan di Danau Ngade Kelurahan Fitu pada Bulan Juni sampai Agustus 2022. Kegiatan meliputi: 1) sosialisasi dengan tujuan untuk menambah wawasan pembudidaya ikan nila dengan menggunakan teknologi bioflok; 2) pelatihan secara langsung cara pembuatan flok di ember, pengukuran flok, penebaran ikan nila, pemeliharaan, dan panen. Hasil dari kegiatan sosialisasi mampu menarik minat peserta, meningkatkan pengetahuan peserta terutama dari kelompok pembudidaya ikan nila yang ada di Danau Ngade terhadap materi bioflok yang diberikan. Terlihat dari interaksi antara peserta dengan narasumber terkait materi yang diberikan selama kegiatan sosialiasi. Sedangkan pada kegiatan pelatihan, pembudidaya mengikuti semua tahapan mulai dari cara pembuatan flok, pengukuran flok, penebaran ikan nila, pemeliharaan, hingga panen. Selama pemeliharaan, praktik yang diberikan adalah 1) manajemen pakan; 2) pengukuran volume flok dan manajemen flok; dan 3) pengukuran beberapa parameter kualitas air seperti pH, suhu, kesadahan, nitrit dan nitrat. Kesimpulan dari kegiatan pengabdian kepada masyarakat ini adalah sosialisasi dan pelatihan yang dilakukan dapat meningkatkan wawasan dan keterampilan peserta terutama pembuddidaya ikan nila dengan menggunakan teknolgi bioflok, mulai dari cara pembuatan flok, pengukuran flok, penebaran ikan nila, pemeliharaan meliputi pemberian pakan dan pengukuran kualitas air, serta panen.
... Compared to the traditional system, the higher BOD concentrations in the BFT treatments were due to bio oc development; bio ocs have oxygen demand in the water(Kuhn 2012). However, BOD values estimated in the present study were in the acceptable ranges for sh cultivation, as suggested in previous studies(Das 1997;Deka 2015).Floc volume is considered as the fundamental marker of bio oc formation(Avnimelech 2012). The oc developed in the BFT treatments likely in uenced alkalinity and hardness in the BFT system with sh excretions concentrating residues and the metabolic activity of the microorganisms in the water(Lee et al. 2013). ...
Effect of stocking density on water quality, growth, nutritional composition and hematological parameters of Ompok pabda reared in traditional and biofloc technology system
Preprint
Full-text available
  • Dec 2022
Biofloc technology (BFT) is nowadays considered as eco-friendly approach being used for fish and shellfish production. The present investigation aimed at comparing water quality, as well as immune responses, nutritional condition and production of Ompok pabda between the traditional culture system with stocking density of 17 (TS 1 ), 22 (TS 2 ) and BFT system (C: N ratio of 20:1; molasses as carbon source) with 17 (BFTS 1 ), 22 (BFTS 2 ), 27 (BFTS 3 ) fish of 0.30 ± 0.001 g/m ² ; the fishes were reared with feeding a commercial diet at 10 − 3% of their body weight for 90 days in tanks. There was significant (p < 0.05) variation in water quality parameters including dissolved oxygen, pH, total ammonia nitrogen (TAN) between the traditional and BFT tanks. The fishes of the BFTS 1 had the highest specific growth rate (SGR, 4.11 ± 0.17%/day) and survival (98.33 ± 2.89%) while the TS 2 had the lowest SGR (3.51 ± 0.05) and survival (86.67 ± 5.03%). The protein, lipid, essential amino acids, monounsaturated fatty acid and polyunsaturated fatty acid contents were found higher in the BFT-reared fishes compared to the TS-reared fishes. The fishes of the BFT system had also higher red blood cell (3.28x10 ⁶ /mm ³ ), hematocrit (34.5%), and neutrophil counts (27.30%) than had the TS-reared fishes. Regarding profitability, the BFTS 2 provided the highest benefit-cost ratio (BCR; 1.22 ± 0.04) whereas the TS 1 system had the lowest BCR (0.99 ± 0.04). Altogether, the obtained results points out that the stocking density modulated the rearing environment, and thus, production of O. pabda traditional and BFT systems; considering FCR and BCR values, the stocking density of 22 fish/m ² can be feasible to bring about good economic return of a O. pabda biofloc system.
Dietary protein requirement for tambaqui cultivated in biofloc and clear water systems
Article
Full-text available
This study aimed to compare tambaqui (Colossoma macropomum) juvenile (9.20 ± 0.23 27 g) growth performance, digestive enzymes, and body composition when offered different feed crude protein (CP) levels (24, 28, and 32% CP) in biofloc (BFT) vs. clear water (CW) systems over 60 days in a 2 × 3 factorial experimental design. Water quality was also meas- ured throughout the experiment. Decreased nitrite (P < 0.05) and increased pH, electrical conductivity, nitrate, turbidity, settleable solids, and total suspended solids were observed in the BFT system compared to the CW system (P < 0.05). Tambaqui in the BFT system pre-sented better feed conversion, final weight, weight gain, productivity, specific growth rate, and protein efficiency rates (P < 0.05) and 100% survival for all CP treatments and rearing systems. No differences (P > 0.05) were detected in tambaqui proximal composition and digestive enzymes, except for trypsin, which was higher activity (P < 0.05) in fish reared in the BFT system. No statistical differences concerning performance indices were noted for CP levels, regardless of the rearing system, although the results suggest better tambaqui adaptive capacity in the BFT system, through better use of the natural food produced in this system. This study indicates that feed containing 24% CP may be offered to tambaqui in both systems, although the BTF was more efficient for rearing tambaqui presenting productivity of 3.09 ± 0.21 kg.m−3 compared to 2.18 ± 0.08 kg.m−3 of the CW system.
ẢNH HƯỞNG CỦA MÔI TRƯỜNG NUÔI BIOFLOC LÊN SINH TRƯỞNG VÀ HOẠT TÍNH ENZYME TIÊU HÓA CỦA TÔM THẺ CHÂN TRẮNG (Litopenaeus vannamei) GIAI ĐOẠN ƯƠNG GIỐNG
Article
  • Dec 2022
Nghiên cứu được thực hiện tại Phòng thí nghiệm Wet Lab, Khoa Thủy sản, Trường Đại học Nông Lâm, Đại học Huế nhằm đánh giá khả năng sinh trưởng và hoạt tính enzyme tiêu hóa của tôm thẻ chân trắng Litopenaeus vannamei ương nuôi trong môi trường biofloc với mật độ cao đạt 5.000 con/m3. Tôm giống PL10 được bố trí theo 2 nghiệm thức môi trường ương nuôi khác nhau gồm (i) không có biofloc (ii) có biofloc trong bể ương thể tích 1 m3 với nguồn nước biển có độ mặn 15‰ và thời gian ương nuôi thí nghiệm trong 30 ngày. Nguồn carbohydrate từ rỉ đường được sử dụng để tạo và duy trì biofloc với tỉ lệ C/N = 15. Kết quả nghiên cứu cho thấy biofloc có tác động tăng cường hoạt tính của enzyme tiêu hóa bao gồm amylase và cellulase ở tôm ương nuôi. Nghiệm thức ương nuôi theo công nghệ biofloc tôm đạt giá trị cao hơn về chiều dài (47,20 ± 1,52 mm/con), trọng lượng (0,71 ± 0,08 g/con), tổng số tế bào máu (7,29 ± 0,15 x 106 tế bào/mL) và tỷ lệ sống (85,61 ± 0,61%) so với nghiệm thức ương nuôi không biofloc với các giá trị tương ứng lần lượt là 40,64 ± 2,62 mm/con, 0,52 ± 0,05 g/con, 6,12 ± 0,51 x 106 tế bào/mL, 73,54 ± 0,65% (p < 0,05) Tôm sau ương nuôi trong môi trường biofloc có khả năng chống chịu stress do biến động môi trường về yếu tố pH, nhiệt độ và độ mặn tốt hơn so với nghiệm thức đối chứng. Kết quả nghiên cứu cho thấy tính khả thi trong ương nuôi tôm thẻ chân trắng với mật độ cao trong môi trường biofloc đáp ứng nhu cầu phát triển đối tượng nuôi này hiện nay.
Development of controlled intensive aquaculture systems with limited water exchange and adjusted carbon to nitrogen ratio
Article
Full-text available
Intensive fish culture is possible if the pond is properly aerated and mixed to avoid the creation of anaerobic sites. However, ammonium and nitrite may accumulate under such conditions up to toxic levels. The efficiency of water exchange as a means to flush out those toxic components was computed. A mathematical model relating the concentration of any given residue to the water exchange rate is presented. An optimal water exchange rate should be defined, since the efficiency is lowered with the increase of exchange rate. Another approach is to control inorganic nitrogen levels by inducing microbial protein synthesis through the addition of prescribed amounts of carbonaceous substrates. The basic concepts of intensive aquaculture systems with a limited water exchange rate are reviewed and discussed. (from Authors)
Growth Performance Of Hybrid Bass And Hybrid Tilapia In Conventional And Active Suspension Intensive Ponds
Article
Full-text available
Recently developed, active suspension intensive ponds are based on the idea that fish ponds (aerated and mixed as required for the well-being of the fish) can also serve as water purification units. The present paper compares water quality and fish growth in conventional intensive ponds (daily water exchange 500%), with active suspension intensive ponds (daily exchange 8%). The fish tested were hybrid tilapia (Oreochromis niloticus -xt O. aureus), already known to perform well in active suspension units, and hybrid bass (Morone saxatilis -xt M. chrysops), which is commercially cultured in conventional intensive ponds. Water quality in the two types of intensive ponds differed as a result of the "internal water purification" vs "external water purification" approach. Bacterial development was greater in the active suspension ponds. Several parameters were affected by the different rate of water exchange, including temperature and removal of ammonium. The latter was lower in active suspension ponds due to reduced washout of particles and their associated nitrifying bacteria. Nitrification was greater in tilapia active suspension ponds because of grazing by this fish. Active suspension units operated with less than 2% of the water used in the conventional intensive ponds. Hybrid bass and hybrid tilapia performed similarly well in both types of pond, indicating the economic advantage of culturing them in the water-saving active suspension system. Tilapia graze on suspended particles, leading to additional savings in feed costs. The good performance of hybrid bass in active suspension ponds is herein reported for the first time.
Control and utilization of inorganic nitrogen in fish culture ponds
Article
Full-text available
One of the main obstacles toward the intensification of aquaculture systems is the accumulation of inorganic nitrogen in the water, A solution demonstrated in this work is to control inorganic nitrogen levels through the induction of microbial protein synthesis. This is achieved by adding a carbonaceous substrate, adjusted in a way so as to supply the needed carbon to immobilize all the non-utilized nitrogen. Inorganic nitrogen levels are reduced due to the resulting production of microbial protein. The in situ produced microbial protein is a substitute to the protein added with the feed. Fish growth in the treated ponds was higher than the growth in conventionally fed ponds. Protein utilization was doubled due to the recycling of nitrogen in the pond system, leading to diminution of the deleterious inorganic nitrogen accumulation. The price of feed was reduced to 50-67% of that common in conventional ponds, due both to replacement of protein and limited wash-out of feed.
Studies in circulated fish ponds: Organic matter recycling and nitrogen transformation
Article
Full-text available
Three types of circulated systems slocked with tilapia were studied: tanks: miniponds; and ponds. Water was continually circulated and aerated. Daily drainage of non-suspended material was applied in most systems. The continual circulation and resulting resuspension of the organic particular ma Her led to a very high rate of microbial activity. Organic carbon was efficiently metabolized and utilized in the food chain. Inorganic nitrogen was completely oxidized and accumulated in water as nitrates, unlike conventional ponds. The establish men! of an active nitrifying population took, however, a period of about 3 weeks during which high levels of ammonium and nitrite were built up. The water body was continually aerated, yet local anaerobic conditions developed, especially in non-drained tanks or in miniponds where the plastic bottom was covered by a soil layer. Such conditions led to a less efficient organic carbon metabolism, to reduced nitrification and to denitrifcation. Fish growth seemed to be retarded in systems where denitrifcation took place, indicating that the growth-retarding factor is associated with production of anaerobic metabolites in the pond. The role of daily drainage and a proper aeration system is to avoid formation of anaerobic pockets.
C/N ratio as a control element in aquaculture systems
Article
Full-text available
Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios is a potential control method for aquaculture systems. This approach seems to be a practical and inexpensive means of reducing the accumulation of inorganic nitrogen in the pond. Nitrogen control is induced by feeding bacteria with carbohydrates, and through the subsequent uptake of nitrogen from the water, by the synthesis of microbial proteins. The relationship among the addition of carbohydrates, the reduction of ammonium and the production of microbial proteins depends on the microbial conversion coefficient, the C/N ratio in the microbial biomass, and the carbon contents of the added material. The addition of carbonaceous substrate was found to reduce inorganic nitrogen in shrimp experimental tanks and in tilapia commercial-scale ponds. It was found in tilapia ponds that the produced microbial proteins are taken up by the fish. Thus, part of the feed protein is replaced and feeding costs are reduced. The addition of carbohydrates, or the equivalent reduction of proteins in the feed, can be quantitatively calculated and optimised, as shown here. Approximate parameters were used in this work. Additional research in this field should be directed at gathering the precise data needed for the exact planning of feed composition.
Pond Aquaculture Water Quality Management
Chapter
  • Jan 1998
After meeting the culture animal’s food requirements, low concentration of dissolved oxygen is the next major variable limiting the production of fish, shrimp, and other species in intensive and semi-intensive aquaculture operations. Mechanical aeration is the most effective means of increasing oxygen availability. Aeration is not new to aquaculture, but over the past few years, interest in this technique has increased tremendously. Many fish and shrimp farmers are installing or upgrading aeration systems, and many companies are selling aeration equipment. Most aquatic farmers, aquaculture aeration equipment manufacturers, researchers, and extension workers have a poor understanding of the fundamentals of aeration, and as a result, they have unrealistic expectations of aerator performance. This is unfortunate because there is a large body of literature and experience on the design, performance, and use of aeration systems in the aquaculture industry.
Pond Aquaculture Water Quality Management
Chapter
  • Jan 1998
It is tempting to view the production of fish, crustaceans, and other aquatic animals in ponds as an inelegant and archaic method of aquaculture. Although pond aquaculture is certainly an ancient method of growing aquatic animals, it is anything but inelegant. Pond aquaculture is generally the most profitable approach to growing aquatic animals because nature provides many of the resources needed to grow the crop. When pond aquaculture is conducted properly, the aquaculturist manages the pond in harmony with natural processes, and surprisingly high yields of food are possible with relatively little technological intervention. In fact, the only water quality management technology that is commonly used in pond aquaculture is mechanical aeration to supplement natural supplies of dissolved oxygen. It is this—the low level of technological intervention needed to obtain good levels of food production—that is the basis for the economic viability of pond aquaculture.