BIOFLOC
Biofloc Fish Farming
Biofloc technology
What is biofloc?
Biofloc is the macro-aggregation of bacteria, algae, detritus and other decomposed components associated with extracellular polymeric substances. It is the combination of bacteria, diatoms, zooplankton, protozoa, macro-algae, faeces, uneaten feed, and exoskeleton from dead organisms.
What is biofloc technology (BFT)?
BFT is an innovative and cost-effective technology. It is based on the principle of waste nutrients recycling, in particular nitrogen, into microbial biomass that can be used as feed by the cultured animals. Heterotrophic bacteria are stimulated to grow by controlling the C:N ratio in the water through the modification of the carbohydrate content in the feed or by the addition of an external carbon source in the water, so that the bacteria can assimilate the waste ammonium for new biomass production. Hence, ammonia can be maintained at a low and non‐toxic concentration. Biofloc Technology (BFT) is considered as new “blue revolution” since nutrients can be continuously recycled and reused in the culture medium, benefited by the minimum or zero-water exchange.
Advantages of biofloc
a) Improved water quality control
b) Improved water use efficiency
c) Improved biosecurity
d) Increased land-use efficiency
e) Improved feed conversion
f) Reduced sensitivity to light fluctuations
Disadvantages of biofloc
a) Start-up period required
b) Continuous aeration is required to keep the floc in suspension
Tank set up
Tanks are constructed from a variety of materials like concrete, RCC, plastic, fiberglass reinforced plastic, ferro-cement, HDP liners etc.
The desired characteristics of tanks for biofloc systems are:
(1) Smooth interior surface to prevent abrasion
(2) Non-toxic surfaces
(3) Durability and profitability
(4) Long life
(5) Ease in cleaning and sterilization
(6) Non-corrosive
(7) Affordability
Round tanks are commonly used as velocity, circulation and mixing pattern are excellent and water quality tends to be more uniform
The suitable size of the tanks varies from 5000 L to 50000 L with an average depth of 1.5m.
The tanks should be constructed on a raised platform of 1.5 ft made of brick and cement work.
The raised platform need to be installed with bottom slop towards centre and a central drainage pipe need to be installed and will be connected to a sump where the sludge formed in the BFT can be drained when excess.
Normally tanks have a wire galvanized iron mesh framework upon which 2 layers of tarpaulin can be attached with the help of tagging line.
The preferred thickness of tarpaulin used is 450-600 grams per square meter (GSM).
Aeration
The tanks should be equipped with proper aeration facilities.
A tank of 10000 L need to have 8-10 aeration points.
For the best performance, it is advised to have 12 points of which, 8 will touch the bottom and 4 will be in the column.
Oxygen supply per line will be 5L/Min to ensure proper aeration.
Water preparation
Method 1
For 15000 Litres of fresh water 150 Litres of inoculum is required for the floc development
Step 1 Take clean tub/can with 150 Litres of water and continue vigorous aeration
Step 2 Add 3 Kg of pond soil + 1.5 gm of Ammonium sulphate /Urea + 30 gm of carbon source (Jaggery /Wheat flour /Tapioca flour)
Step 3 Mix it well with water in tub and provide adequate aeration
Step 4 The inoculum will be ready after 24-48 hrs and it can be transferred to main tank
Daily addition of carbon source is required for the development of floc.
Method 2
Step 1 Take clean tub/can with 130 Litres of water and continue vigorous aeration
Step 2 Add 20 Litres of pond water + 30 gm of carbon source (Jaggery /Wheat flour /Tapioca flour) + 10 gm of probiotic (with Bacillus Sp., Aspergillus Sp. etc with a total concentration of 10x109 CFU/gm)
Step 3 Mix it well with water in tub and provide adequate aeration
Step 4 The inoculum will be ready after 24-48 hrs and it can be transferred to main tank
Ideal Volume of Floc for shrimp is 10-15 ml/L and for Fish 25-35 ml/L
Species selection & stocking densities
Criteria for selection of candidate species for BFT
· Fast growth
· Short food chain
· Better feed conversion efficiency
· Ready acceptance of compounded feeds
· Ability to tolerate high density
· Ability to assimilate the biofloc
· Tolerance to high amount of suspended solids
· Tolerance to higher nitrogen compounds (TAN, nitrite-N, nitrate-N)
· Easy availability of seed
· Disease resistance
· Consumer acceptance and marketability
· Domestic consumption versus export
Some of the species that are suitable for BFT are:
· Air breathing fishes: Singhi (Heteropneustes fossilis), Magur (Clarias batrachus), Pabda (Ompok pabda), Anabas/Koi (Anabas testudineus), Pangasius (Pangasianodan hypophthalmus)
· Non air-breathing fishes: Common Carp (Cyprinus carpio), Rohu (Labeo rohita), Catla catla (Catla), Pearl spot (Etroplus suratensis), Tilapia (Oreochromis niloticus), Milkfish (Chanos chanos)
· Shellfishes: Vannamei (Litopenaeus vannamei) and Tiger Shrimp (Penaeus monodon)
After 4-5 days of acclimatization, the fishes can be stocked into BFT.
The tanks should be ready with a minimum amount of biofloc (5-10 ml/l) developed before stocking the fishes.
Stocking density of different species for BFT are: Tilapia 35-45 kg/m3, Shrimp 15-25 kg/m3, Carps 40 kg/m3.
The stocking density can be a maximum of 150 no/ m3 in case of Tilapia as the culture of species is under strict regulation.
Carbon: Nitrogen manipulation
Important step in BFT development is Carbon: Nitrogen ratio (C: N) manipulation.
Carbon to Nitrogen Ratio (CN Ratio) is a process of controlling the amount of Nitrogen in water.
Most popular CN ratios are 10:1 and 15:1, which means in CN Ratio 10:1, you need 10 Carbon Sources to kill 1 Nitrogen.
In aquaculture, CN Ratio is calculated based on Protein Percentage of Feed and Total Ammonia Nitrogen (TAN)
C:N content in the feed
C: 4 kg of feed × 0.9 (90% dry matter) × 0.7 (30% of fish assimilation or 70% of waste that
remains in water)/2 (carbon content of the feed is ~50% based on dry matter) = 1260 g of C
N: 4 kg of feed × 0.9 (90% dry matter) × 0.7 (30% of fish assimilation or 70% of waste that
remains in water) × 0.3 (30% crude protein content of feed)/6.25 (constant) = 121 g of N.
The results indicated a ~10:1 C:N ratio of feed.
Adjusting the C:N ratio
If you want C:N ratio of 20:1, 121 g of N in feed × 20 = I need 2420 g of C.
But you already have 1260 g of C (calculated in feed). So 2420 g–1260 g of C
You really need 1160 g of C.
If the molasses has 50% of carbon content (based on dry matter), 1 kg of molasses represents 500 g of carbon.
So, 1160 g of carbon requirement will represent 2320 g (or 2.3 kg) of molasses (applied daily until biofloc maturation ).
C N Ratio Based on Total Ammonia Nitrogen (TAN)
Let’s consider the Total Ammonia Nitrogen (TAN) in the BIOFloc Tank is 2 PPM (Parts Per Million or Milligram Per Liter)
For a 10,000 Liter Tank it will be 10,000 x 2 = 20,000 mg TAN
Lets convert mg to gram = 20000 mg / 1000 = 20 g TAN
· For C:N Ratio 10:1 = 10 x 20 = 200 gram Carbon needed
· For C:N Ratio 12:1 = 12 x 20 = 240 gram Carbon needed
· For C:N Ratio 15:1 = 15 x 20 = 300 gram Carbon needed
Water quality parameters
WATER QUALITY PARAMETERS SUITABLE FOR CULTURE IN BFT
Parameters | Range |
pH | 7.5 – 8 |
Temperature | 26 – 34 °C |
Dissolved oxygen | 5 – 8 mg/L |
Free carbon dioxide | 6 – 9 mg/L |
Alkalinity | 120 – 280 ppm |
Ammonia | <0.5 ppm |
Nitrite | <0.3 ppm |
Nitrate | <60 ppm |
Total dissolved solids Total suspended solids | 600- 1500 ppm < 400 ppm |
Biofloc volume | 25-40 ppm |
Feeding management
In BFT, fish need to be fed at a lower ration than conventional system.
It can be 5-10% lower protein percentage.
The feeding percentage can be reduced from 6% of body weight initially to 1.2 % of body weight towards end of culture period.
The younger ones need to be fed with higher ration and small size feed.
Commercial floating feed is highly recommended for feeding in BFT as water quality is a major concern in this system.
Protein requirement of various finfishes in BFT
The protein requirements of some of the commercially important species are given below:
Species | Protein requirement |
Indian major carps | 25-30 % |
Pangasius | 28 -30% |
Magur | 30-35% |
Koi | 30-35% |
Tilapia | 25-30% |
Shrimp | 30-35 % |
The mouth size of the fishes should be matching with size of the feed, hence the feed size is also important feature in efficient feeding in BFT.
The estimated ration requirements at different body weights of fish in BFT are given in the following Table.
Body weight | Feeding ration/ weight | Feed size |
5-20 gm | 7- 6 % | 1-1.5 mm |
20-50 gm | 6-5 % | 1.5-2.0 mm |
50-100 gm | 5-4 % | 2.0-3.0 mm |
100-250 gm | 4- 3.5 % | 3.0-4.0 mm |
250 – 500 gm | 3.0- 2.5 % | 3.0-4.0 mm |
500- 1000 gm | 2.0-1.8 % | 3.0-4.0 mm |
Do’s and dont’s in feeding
· Do not overfeed fishes
· Regulate the daily ration into 3 equal intervals
· Reduce the feeding during winter
· If there is excess floc, reduce feeding and carbon addition
· Excess floc should be removed through sludge discharge systems
· Feed fishes with balanced nutrition
· Strictly observe the feeding behaviour
· If fishes are showing lack of intake, reduce the ration and regulate the feeding
Disease management
Fin rot
Clinical signs: Frayed fins, Edges of fins turn black or brown
Causative agent: Pseudomonas flourescens
Treatment: Improve water quality
Periodic sludge removal,
Dip treatment with KMno4 (1 gm in 10 litre water for 5 minutes)
Dropsy
Clinical signs: Swollen belly, Bulging eyes, Pale gills, Scales protrusion
Causative agent: Aeromonas sp.
Treatment: Mix oxytetracycline (70-80 mg) to 1 Kg of feed and give it for 7 days
Columnaris
Clinical signs: Brown areas on gills, Grey patches are seen over head and caudal fin
Causative agent: Flavobacterium columnare
Treatment: 1. Tetracycline @70-80 mg/kg of body weight of fish with feed for 7-10 days
2. Bath treatment using copper sulphate (1 gm in 2 litre water) for 3-4 days
3. Bath treatment using table salt @ 15% (150gm per litre water) for 15 minutes
Branchiomycosis (Gill rot)
Clinical signs: Excessive mucus secretion in gill, frayed appearance of gill
Causative agent: Branchiomyces sanguinis or B. demigrans
Treatment: 1. Maintain water quality
2. Tetracycline @ 50-60 mg/kg of body weight of fish with feed for 5-7 days
3. Bath treatment with 1-2 ppm Benzylokonium chloride for 1 hour.
4. Add 1-2 ppm KMnO4 in pond water, followed by liming @ 200kg/ha in split doses
Argulosis
Clinical signs: Parasites are visible to naked eye attached to head and fin rays, haemorrhagic spots found in chronic cases
Causative agent: Argulus sp.
Biofloc Equipment
· Biofloc tarpauline tank
· Aeration pump
Air stones
· Air tubes
· Imhoff cone
· Biofloc test kits and meters
· Probiotics
· Calcium carbonate
· Raw sea salt
Log Book
Create a tank
Tank Name:…………………….
Diameter: ………………………
Height: …………………………
Bottom slope height:…………….
Water capacity: …………………
Water preparation date: ………………
Fish species: ……………………………
Stocking density: ………………………
Probiotics used: ……………………….
Stocking date: …………………………
Feed given: ……………………………
Remarks: ……………………………...
SAVE |
References
NFDB (2020), Recent trends in aquaculture, Biofloc fish Culture. Available at: https://nfdb.gov.in/PDF/02_Biofloc%20Culture_Eng.pdf
Panigrahi A, Otta S. K., Kumaraguru Vasagam K. P., Shyne Anand P. S., Biju I. F., and Aravind R. Training manual on Biofloc technology for nursery and growout aquaculture, CIBA TM series 2019 No. 15, 172 pp.
ICAR-CIFE (2020), Training manual on Biofloc technology for intensive farming practices.
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