With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements:

Biofilters provide waste treatment by removing uneaten fish feed.

Biofilters convert ammonia present in fish waste to nitrate.

Biofilters increase phosphorus as nutrient for fish in water.

How many of the statements given above are correct? (UPSC Prelims 2023)

Question

The correct answer is [B] Only two.

Statement 1 – Correct: One of the key components of Recirculating Aquaculture Systems (RAS) is Mechanical Filtration which removes solid waste, such as uneaten feed and feces, from the water.
Statement 2 – Correct: This is the primary and undisputed biological function of a biofilter. Through the process of nitrification, specialized aerobic bacteria (Nitrosomonas and Nitrobacter) convert toxic ammonia (NH₃) excreted by fish into nitrite (NO₂), and subsequently into relatively harmless nitrate (NO₃).
Statement 3 – Incorrect: Biofilters are not designed to \"increase phosphorus\" as a nutrient. In an RAS, phosphorus primarily enters the system through fish feed. Excessive phosphorus is actually a pollutant that can lead to eutrophication or algal blooms within the system. Instead of increasing it, management strategies in an RAS often focus on removing excess phosphorus through chemical precipitation or solids removal.

GKToday Admin · Accepted Answer

Only two The correct answer is [B] Only two.

Statement 1 – Correct: One of the key components of Recirculating Aquaculture Systems (RAS) is Mechanical Filtration which removes solid waste, such as uneaten feed and feces, from the water.
Statement 2 – Correct: This is the primary and undisputed biological function of a biofilter. Through the process of nitrification, specialized aerobic bacteria (Nitrosomonas and Nitrobacter) convert toxic ammonia (NH₃) excreted by fish into nitrite (NO₂), and subsequently into relatively harmless nitrate (NO₃).
Statement 3 – Incorrect: Biofilters are not designed to \"increase phosphorus\" as a nutrient. In an RAS, phosphorus primarily enters the system through fish feed. Excessive phosphorus is actually a pollutant that can lead to eutrophication or algal blooms within the system. Instead of increasing it, management strategies in an RAS often focus on removing excess phosphorus through chemical precipitation or solids removal.

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