Fish disease refers to a variety of health issues that can affect fish, often caused by pathogens such as bacteria, viruses, fungi, or parasites. These diseases can lead to symptoms like abnormal swimming, lesions, or changes in behavior. Environmental factors, such as poor water quality or overcrowding, can also contribute to the onset of diseases in fish populations. Preventing fish disease involves maintaining a clean habitat, ensuring proper nutrition, and monitoring water conditions. Regular health checks and quarantining new fish can help reduce the spread of illness. Understanding common diseases, like ichthyophthirius or fin rot, is essential for effective management and treatment.