Biofloc technology has gone from a research curiosity to one of the most asked-about topics in Indian fisheries examinations — and for good reason. ICAR-CIBA, Chennai, has spent years turning it into a field-ready system for shrimp and fish farmers, with its own standard operating procedure, its own microbial consortium, and frontline demonstrations across the country. If you are preparing for ICAR-JRF/SRF, state fisheries service exams, or university entrance tests, the numbers and concepts below are exactly the kind of detail examiners love to test.
This set gives you 20 exam-style multiple-choice questions on biofloc technology, built around published ICAR-CIBA work. Attempt them honestly first, then check the answer key — every answer carries a short explanation so a wrong answer still teaches you something.
Biofloc in 60 Seconds: The Revision Table
Read this table once before attempting the questions. Almost every answer below comes from it.
| Fact | Detail (ICAR-CIBA record) |
|---|---|
| What biofloc is | Aggregates of heterotrophic bacteria and other microbes that convert nitrogenous waste into protein-rich microbial biomass, which the cultured animals eat |
| Key control | Manipulating the carbon-to-nitrogen (C:N) ratio so the system becomes bacteria-dominated rather than algae-dominated |
| C:N ratio in CIBA’s P. indicus study | 12:1, maintained with a blend of carbohydrate sources |
| Common carbon sources | Molasses, rice bran, atta and similar carbohydrates |
| How floc volume is measured | Imhoff cone (ml of floc per litre) |
| CIBA nursery stocking density | 3,000–8,000 post-larvae per m³ |
| CIBA nursery survival | 90–98% |
| Juvenile size at nursery harvest | 300–600 mg |
| Cost of production | 15–20% lower than conventional nursery rearing (CIBA Balasore demonstration) |
| CIBA’s biofloc consortium | CIBAFLOC |
| Water exchange | Zero or minimal — the system recycles water in situ |
| Risk of excess degraded floc | Hydrogen sulphide (H2S) production at the pond bottom, which is highly toxic |
| Best-suited species | Bottom-dwelling species such as shrimp and tilapia |
| Origin of the technology | Developed in the 1990s to conserve feed inputs and use wastewater in production |
| Conventional nursery stocking | 300–3,000 nos. per m³ |
| High-tech BFT/RAS nursery stocking | 2,000–20,000 nos. per m³, needing more technical control |
| Supporting agency for CIBA’s frontline demos | Department of Biotechnology, Government of India |
The 20 MCQs
Q1. Biofloc technology primarily works by developing a dense community of which type of microbes?
(a) Autotrophic algae (b) Heterotrophic bacteria (c) Nitrifying fungi (d) Photosynthetic protozoa
Q2. The single most important ratio manipulated to develop biofloc is:
(a) C:P ratio (b) N:P ratio (c) C:N ratio (d) Ca:Mg ratio
Q3. In ICAR-CIBA’s bio-augmentation study on Indian white shrimp (Penaeus indicus), the C:N ratio was maintained at:
(a) 5:1 (b) 10:1 (c) 12:1 (d) 20:1
Q4. Which of the following is commonly used as a carbohydrate (carbon) source in biofloc systems?
(a) Urea (b) Molasses (c) Lime (d) Formalin
Q5. Floc volume in a biofloc system is measured using a/an:
(a) Secchi disc (b) Imhoff cone (c) Refractometer (d) DO meter
Q6. In ICAR-CIBA’s frontline demonstrations, biofloc nursery rearing of P. vannamei was stocked at:
(a) 300–800 PL/m³ (b) 1,000–2,000 PL/m³ (c) 3,000–8,000 PL/m³ (d) 20,000–30,000 PL/m³
Q7. Survival reported in CIBA’s biofloc nursery demonstrations was:
(a) 40–50% (b) 60–70% (c) 90–98% (d) 100%
Q8. Juveniles from CIBA’s biofloc nursery system reached what size at harvest?
(a) 30–60 mg (b) 300–600 mg (c) 3–6 g (d) 10–15 g
Q9. CIBA reported the cost of production in its biofloc nursery system to be:
(a) 15–20% lower than conventional rearing (b) 15–20% higher (c) Equal to conventional rearing (d) Twice as high
Q10. The microbial consortium developed by ICAR-CIBA for floc generation and water quality management is called:
(a) CIBAFLOC (b) CIBA-PRO (c) BIOFISH (d) FLOCSHIELD
Q11. Biofloc systems are characterised by which water-exchange regime?
(a) Continuous flow-through (b) Daily 100% exchange (c) Zero or minimal exchange (d) Weekly 50% exchange
Q12. Excess, degraded floc at the pond bottom is dangerous mainly because it produces:
(a) Oxygen (b) Hydrogen sulphide (H2S) (c) Calcium carbonate (d) Methane only
Q13. Which species group is best suited to biofloc production?
(a) Surface-feeding carps only (b) Bottom-dwelling species such as shrimp and tilapia (c) Coldwater trout only (d) Marine ornamental fish only
Q14. Biofloc technology was developed in the 1990s primarily to:
(a) Increase pond depth (b) Conserve feed inputs and utilise wastewater (c) Replace all aeration (d) Eliminate the need for seed
Q15. Conventional (non-biofloc) nursery rearing of penaeid shrimp is typically stocked at:
(a) 300–3,000 nos./m³ (b) 20,000–50,000 nos./m³ (c) 100–200 nos./m³ (d) 1–10 nos./m³
Q16. High-tech biofloc/RAS nursery systems may stock post-larvae at:
(a) 100–500 nos./m³ (b) 2,000–20,000 nos./m³ (c) 50,000–100,000 nos./m³ (d) 5–50 nos./m³
Q17. In a biofloc system, heterotrophic microbes convert nitrogenous waste — mainly total ammonia nitrogen (TAN) — into:
(a) Nitrate gas (b) Microbial protein eaten by the cultured species (c) Lime (d) Oxygen
Q18. Biofloc reduces feed cost because:
(a) Fish stop eating altogether (b) The flocs themselves are a protein source consumed by the animals (c) Feed becomes free (d) Stocking density falls
Q19. Which institute developed the standard operating procedure (SOP) for biofloc nursery rearing demonstrated across India?
(a) ICAR-CIFA, Bhubaneswar (b) ICAR-CIBA, Chennai (c) ICAR-CMFRI, Kochi (d) ICAR-CIFT, Kochi
Q20. CIBA’s frontline demonstrations of biofloc nursery technology were conducted with support from:
(a) The World Bank (b) Department of Biotechnology, Government of India (c) FAO headquarters (d) Private feed companies only
Answer Key with Explanations
1. (b) Biofloc is a dense heterotrophic bacterial community developed through C:N manipulation; the system becomes bacteria-dominated rather than algae-dominated.
2. (c) Raising the carbon-to-nitrogen ratio stimulates heterotrophic bacteria to assimilate nitrogenous waste.
3. (c) CIBA’s P. indicus bio-augmentation study maintained a C:N ratio of 12:1 using a blend of carbohydrate sources.
4. (b) Molasses (along with rice bran and atta) is a standard carbohydrate source added to raise the C:N ratio.
5. (b) Floc volume is read in an Imhoff cone — CIBA’s training covers measuring biofloc with the Imhoff cone.
6. (c) CIBA’s Balasore demonstration stocked 3,000–8,000 PLs/m³.
7. (c) The same demonstration reported 90–98% survival.
8. (b) Juveniles reached 300–600 mg in the CIBA demonstration.
9. (a) CIBA reported a 15–20% lower cost of production versus conventional nursery rearing.
10. (a) CIBAFLOC is ICAR-CIBA’s biofloc-based microbial consortium.
11. (c) Biofloc is a zero/minimal-water-exchange system; water quality is managed in situ.
12. (b) Excess degraded floc generates toxic H2S at the pond bottom, so routine sludge removal matters.
13. (b) Bottom-dwelling species like shrimp and tilapia are best suited, since they continuously consume the floc.
14. (b) The technology emerged in the 1990s to conserve feed inputs and use wastewater during production.
15. (a) Conventional nursery rearing uses 300–3,000 nos./m³, versus 2,000–20,000 in high-tech BFT/RAS nurseries.
16. (b) High-tech BFT/RAS nursery systems stock 2,000–20,000 nos./m³ and need more technical control.
17. (b) Heterotrophic microbes convert nitrogenous waste into microbial protein — protein is used both as feed and as floc.
18. (b) Because the animals eat the protein-rich floc, supplementary feed requirement and cost fall.
19. (b) ICAR-CIBA, Chennai, developed the BFT SOP and demonstrated it in the field.
20. (b) CIBA’s frontline demonstrations were supported by the Department of Biotechnology, Government of India.
How to Use This Set
- Score yourself honestly: 17–20 is exam-ready; 13–16 means revise the table above once more; below 13, re-read the explanations and retry tomorrow.
- Watch for the traps: examiners swap the C:N value (12:1, not 20:1), the stocking densities (conventional vs biofloc), and the consortium name (CIBAFLOC).
- Link the concepts: biofloc questions pair naturally with water-quality questions — ammonia, dissolved oxygen and sludge management all come back in the same paper.
Keep Practising
Try our other question-bank sets: Shrimp Farming in India: 20 MCQs, Water Quality MCQs: 20 Questions, 20 Fish Disease MCQs, and Catla vs Rohu vs Mrigal: 20 MCQs.
Official Sources
- ICAR news: Biofloc based Shrimp Nursery Technology demonstrated by ICAR-CIBA (Balasore, 27 September 2018) — icar.org.in/en/node/3105
- ICAR news: Training Programme-cum-Workshop on Biofloc-based High Density Nursery and Grow-out Shrimp/Fish Farming, Kovalam (14 June 2022) — icar.org.in (training report)
- Panigrahi et al., Biofloc based nutrient dense culture system for nursery and grow-out farming of Penaeus vannamei, Indian Journal of Fisheries 64 (Special Issue), 2017
- Panigrahi et al., Bio-augmentation of heterotrophic bacteria in biofloc system for Indian white shrimp Penaeus indicus (ICAR-CIBA study; C:N 12:1)
Figures in this post are taken from the ICAR-CIBA sources above. If you spot a correction, tell us — accuracy matters more than speed here.