Fish can get sick just like any other living creature, although it is less likely with proper aquarium management. It is important to watch for signs of any potential diseases in order to prevent their spread. Common signs of fish diseases include lethargy, loss of appetite, clamped fins, gill abnormalities, changes in color, abdominal swelling, ulcers, lesions, rapid breathing, etc. Common fish diseases include bacterial infections, fungal infections, parasites, and viral infections. Bacterial infections can cause ulcers, fin and tail rot, cloudy eyes, popeye, and more. Fungal infections can manifest as white growths on the skin or fins. Parasites like ich, Columnaris, and flukes, can cause white spots on the body and gills, difficulty breathing, and more severe infections can lead to death. Viral infections can cause general symptoms like loss of appetite and lethargy, but also can cause more severe issues like hemorrhaging, fin rot, and other infections. To treat a disease, it is important to accurately identify it and provide the right treatment. In many cases, this may mean removing the sick fish from the main tank to provide prevent any spread to other fish. Depending on the issue, antibiotics or other treatments may be required. In extreme cases, euthanasia may be necessary to prevent suffering.