Bacterial or Viral infections cause various problems with the infected fish usually resulting in death. They are mostly contagious and can spread through an aquarium very quickly if left untreated. Some common Bacterial Diseases include Dropsy, Fin Rot, Mouth Fungus, and Hole-in-the-head. Most of these are difficult to treat and prevention is the best solution.
Some common signs of bacterial infections are that the fish may appear sluggish, it may hide and not eat. It might have a swollen body red streaks or spots on it's body. The infected fish might have eyes that are cloudy or protruding. It might also have torn or frayed fins. If a fish is showing any of these signs then there is a good chance it is infected with a bacterial disease.
Dropsy: The fish will have a swollen body with raised scales making it look like a pine-cone. If caught early it can be treated with Maracyn-Two or Furan-2.
Fin Rot: The fish will have frayed and damaged fins. It can be treated with Maracyn-Two, Furan-2 or E.M. Erythromycin.
Mouth Fungus: The fish will have white growths around the mouth. It can be treated with Furan-2 or E.M. Erythromycin.
Hemorrhagic Septicemia: The fish will have red spots or streaks on it body and fins. It can be treated with Furan-2 or E.M. Erythromycin.
Hole-in-the-head: The fish will have ulcers that look like holes in the head region. It can be treated with Furan-2.