With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements: 1. Biofilters provide waste treatment by removing uneaten fish feed. 2. Biofilters convert ammonia present in fish waste to nitrate. 3. Biofilters increase phosphorus as nutrient for fish in water. How many of the statements given above are correct?

Recirculating Aquaculture Systems (RAS) use biofilters as a key component for water treatment. Statement 1 is incorrect. Biofilters primarily treat dissolved waste products, particularly nitrogenous compounds. Solid wastes, such as uneaten fish feed and feces, are typically removed by mechanical filters (like drum filters or settling tanks) before the water reaches the biofilter. While the decomposition of uneaten feed produces substances that the biofilter treats, the biofilter itself does not remove the solid feed. Statement 2 is correct. The main function of a biofilter in RAS is nitrification, which is the biological process where beneficial bacteria convert toxic ammonia (excreted by fish and from decomposition) first into nitrite and then into much less toxic nitrate. This is essential for maintaining water quality suitable for fish. Statement 3 is incorrect. Biofilters are designed to remove or convert waste products, not increase nutrients for fish. While phosphorus is present in fish feed and waste, biofilters are primarily focused on managing nitrogen. Systems for nutrient addition for fish involve providing high-quality feed, not manipulating waste products in the water circuit.