Question 1

What is Biofloc Technology (BFT) and how does it benefit fish farming?

Accepted Answer

Biofloc Technology is a sustainable aquaculture system where beneficial heterotrophic bacteria convert toxic ammonia waste into nutrient-rich microbial protein (floc). It operates with zero or minimal water exchange, dramatically reducing water usage and feed costs while enabling high stocking density in tarpaulin tanks.

Question 2

How do I calculate and dose molasses to maintain the 15:1 C:N ratio in Biofloc?

Accepted Answer

To maintain a 15:1 Carbon-to-Nitrogen ratio, add organic carbon (like molasses or sugar) based on the crude protein percentage and weight of the daily feed. For example, for 1 kg of 32% protein feed, roughly 100-150g of pre-dissolved molasses is required. You can use our interactive Biofloc Carbon Calculator on this site to get exact dosage amounts.

Question 3

What is the ideal Floc Volume Index (FVI) in an Imhoff cone?

Accepted Answer

For tilapia and catfish, the target floc volume is 25 ml to 35 ml per litre of tank water measured after 30 minutes of settling in an Imhoff cone. If floc volume exceeds 40 ml/L, run sludge drain valves or reduce carbon dosing; if below 15 ml/L, boost probiotic and carbon supplementation.

Question 4

Why is continuous 24/7 aeration critical for Biofloc tarpaulin tanks?

Accepted Answer

Biofloc bacteria and dense fish populations both consume large amounts of oxygen. If aeration stops for even 30–60 minutes, Dissolved Oxygen (DO) plummets, causing floc to die and collapse into toxic sludge, resulting in immediate fish mortality. Always maintain backup power or air ring blowers.

Question 5

What are the core filtration stages in a Recirculating Aquaculture System (RAS)?

Accepted Answer

A complete commercial RAS includes: 1) Swirl Separator/Drum Filter for solid waste removal, 2) Moving Bed Biofilm Reactor (MBBR) for nitrifying bacteria (converting Ammonia to Nitrite to Nitrate), 3) Protein Skimmer/Degasser for CO2 stripping, and 4) UV Sterilizer/Ozone for pathogen disinfections before re-entering culture tanks.

Question 6

How does the MBBR biofilter convert toxic Ammonia into harmless Nitrate?

Accepted Answer

The MBBR biofilter holds plastic media (K1/K3/MBBR media) colonized by two strains of nitrifying bacteria: Nitrosomonas (converts toxic Total Ammonia Nitrogen into toxic Nitrite) and Nitrospira/Nitrobacter (converts Nitrite into relatively harmless Nitrate). Constant air fluidization keeps media suspended.

Question 7

What water flow turnover rate is recommended for intensive RAS?

Accepted Answer

In commercial fish culture setups, the entire water volume of culture tanks should pass through the filtration loop at least 1.0 to 1.5 times per hour. High stocking density (60-100 kg/m³) requires even faster circulation rates to prevent ammonia accumulation.

Question 8

What is Feed Conversion Ratio (FCR) and what is considered a good value?

Accepted Answer

FCR measures how many kilograms of feed are required to grow 1 kilogram of fish body weight (FCR = Total Feed Given ÷ Total Weight Gained). An FCR of 1.10 to 1.30 is considered excellent in intensive commercial aquaculture.

Protein Skimmer in RAS: Essential for Clean Water

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