Answer:(a) Only one.
Let's analyze each statement:
Biofilters provide waste treatment by removing uneaten fish feed: This statement is incorrect. Biofilters primarily function to remove toxic substances, such as ammonia and nitrite, from the water. They do not specifically target uneaten fish feed.
Biofilters convert ammonia present in fish waste to nitrate: This statement is correct. Biofilters play a crucial role in the nitrogen cycle of Recirculating Aquaculture Systems (RAS). They house beneficial bacteria that convert toxic ammonia (produced from fish waste) into nitrate, which is less harmful to fish.
Biofilters increase phosphorus nutrient for fish in water: This statement is incorrect. Biofilters do not directly increase phosphorus nutrient levels in the water. Their main function is related to nitrogenous waste removal rather than phosphorus.