The correct option is that only two of the statements are correct. Statements 1 and 2 are accurate; biofilters indeed aid in waste treatment by breaking down uneaten fish feed and converting harmful ammonia from fish waste into less toxic nitrates through nitrification. However, statement 3 is incorrect because biofilters primarily promote the removal of excess nutrients, including phosphorus, thereby controlling its concentration in water rather than increasing it, which is crucial for maintaining water quality and promoting a healthy aquaculture environment. This understanding is pivotal in aquaculture management as effective biofiltration systems are integral to sustainable practices, directly aligning with the UPSC focus on environmental conservation and resource management.