Costia Necatrix is a parasitic protozoan that is known to cause diseases in fish. It is a dreaded disease-causing organism that can spread rapidly and wipe out an entire fish population. There are a few synonyms for the term Costia Necatrix, including Ichthyobodo Necatrix, Ichthyobodo Infection, and Costia Infection. These synonyms are often used interchangeably, but they all refer to the same parasitic protozoan. It is essential to know these synonyms as it helps in identifying the disease correctly, and appropriate treatment can be provided to the affected fish. Identifying the disease early on and administering the right treatment is crucial in preventing the spread of the disease to other aquatic animals.