BFT is the intensive fish culture technology being practiced throughout the world.

1. BIOFLOC TECHNOLOGY
(BFT)
BY
MARYAM HAMEED
ASSISTANT DIRECTOR FISHERIES

2. Definition
“The Biofloc is a protein rich macro aggregate of organic material and
micro-organisms”
• It is a technique of enhancing water quality in aquaculture through
balancing carbon and nitrogen in the system.
• The microbial particles can provide important nutrients such as
protein , lipids , amino acids and fatty acids
• Biofloc might also contain immuno-stimulatory compounds since
biofloc technology deals with bacteria and bacterial products

3. Goals
• To produce more aquaculture products with
minimum usage of the basic natural
resources of water and land
• To develop environment friendly sustainable
aquaculture systems
• To build up systems providing an equitable
cost/benefit ratio to support economic and
social sustainability.
The three
fundamentals for
sustainable
aquaculture
development that
can be met by
biofloc
technology are:

4. Basic Requirements
• The control of biofloc in ponds during operation
• High stocking density
• High aeration
• Lined ponds
• Suitable feed according to the species
• Molasses/ Starch/ Wheat flour/ Gurr etc. (As source of carbon)

5. Principle
• Limit water exchange
• Organic residues accumulate
• Mix and aerate
• Ideal conditions for bacteria
• Bacteria control water quality
• Fish eat bacteria
• Feed is recycled

6. Step 1
Pond/ tank construction
• Construct a Cemented/ iron-mesh tank of 10,000 liter capacity
• HDPE/ Fiber coated sheet lining

7. Step 2
Water preparation and aeration
• Place minimum 6 air stones / bubble stones in different places of tank
• Fill 1000 liter water into the tank
• Mix 1g/liter salt (raw salt, NaCl, Sea salt et.) in the water and aerate
for 3 hours
• Mix Caco3 @ 0.5g/liter and aerate for 3 days
• Mix molasses/ starch/ sugar/ gur/ wheat flour @ 0.1g/liter

8. Step 3
Probiotics usage
• Mix probiotics (120gm) in the water after 3 hours of molasses mixing

9. Step 4
Floc Development
• Wait for Floc generation 7-15 days
• Measure with cone daily until reached desired quantity (10ml/l)
• Sampling Method
a. 1 liter/ 2 places/ 15cm deep/ between 10-12 am
b. Let it settle for 15-20 minutes
c. Read density of flocs in cone (ml/l)

10. FLOC Development stages (density):
Stage 1 : Floc found but cannot measured
Stage 2 : Floc found in small quantity, < 1.0 ml/litre
Stage 3 : Floc found abundance, 1.0 – 5.0 ml/litre
Stage 4 : Floc found abundance, 5.1 – 10.0 ml/litre
Stage 5 : Floc found abundance, > 10.1 ml/litre

11. Step 5
Introduction of Fish in the system
• Add Fish into the system
• Gradually increase water level and feed fish

12. Step 6
Maintenance
• Check bacteria ratio, pH, TAN (Total ammonia nitrogen), the total
amount of nitrogen in the forms of NH3 and NH4+ in water), TSS
(Total suspended solids), TDS (Total dissolved solids), Temperature,
Nitrate and Nitrite
• Maintain CN ratio ideally 15:1 by adding required amount of molasses
• Drain water from bottom out let to check for settled residue after 10
to 15 days
• Top-up evaporated water
• Sample fish to check growth and health biweekly
• Follow the maintenance steps until harvesting

13. Parameter
Ideal and/or normal
observed ranges
Observations
Dissolved oxygen (DO) Above of 4.0 mg L−1
For correct fish, shrimp, microbiota respiration, and growth
Temperature
28–30° (ideal for tropical
species)
Besides fish/shrimp, low temperatures (~20° C) could affect
microbial development
pH 6.8–8.0
Values less than 7.0 is normal in BFT but could affect the
nitrification process
Salinity
Depends on the cultured
species
0 to 50 ppt
TAN Less than 1 mg L−1
(ideal) Toxicity values are pH dependent
Nitrite Less than 1 mg L−1
(ideal)
Critical parameter (difficult to control). Special attention
should be done, e.g., on protein level of feed, salinity, and
alkalinity
Nitrate 0.5–20 mg L−1
In these ranges, generally not toxic to the cultured animals
Alkalinity More than 100 mg L−1
Higher values will help the nitrogen assimilation by
heterotrophic bacteria and nitrification process by
chemoautotrophic bacteria
Total suspended solids (TSS) Less than 500 mg L−1

14. Advantages
1. Bio-security very good
2. Zero/ minimum water exchange – less than 100% exchange for
whole culture period
3. Production (Carrying capacity): 5-10% better than normal system
4. FCR low – between 1.0 to 1.3
5. Production cost lower by around 15-20 %.

15. Disadvantages
1. High energy input
2. Power failure critical – maximum one hour at any time
3. Full lined ponds – minimum semi- lined