• There are many reasons your saltwater fish may become ill. It may because of a bacterial, a fungal or a parasite infection. The best way to prevent any type of disease to eliminate stress by ensuring stable temperatures and ensuring good water quality. However, if an infection still occurs, knowing what different fish diseases look likes will help you treat infected fish as well as protect the other aquarium's inhabitants.
  
  

Fin Rot

• There are number of diseases caused by different bacteria that can develop in your aquarium. A common bacterial infection is fin rot. When fin rot sets in, the base of your fish's fins will begin to turn red. As the disease progresses, the fins will look as if they are rotting away. In the end stages of the disease, the bacteria will move to the gills of the fish and they will begin to bleed. Fin rot can be treated with an antibiotic added directly to the aquarium. Use 20 to 30 milligrams of antibiotic, which can be purchased at your local pet store, directly to the water for every liter of water in the tank.
  
  

Wasting Disease

• Another common bacterial disease is wasting disease. Wasting disease infects the inside of the fish. Unfortunately, the first sign of outwards symptoms of the disease means it is in the end stages and likely is too late to do anything to save the fish. When symptoms do show, your fish will experience external sores, trouble breathing, appetite loss and loss of scales. The best treatment for wasting disease is prevention. Avoid giving your fish raw shellfish, which may contain the bacteria. There are antibiotics such as kanamycin or erythromycin that can be given, but they will not usually work for a fish that has exhibited symptoms. They will, however, treat other fish who have not demonstrated symptoms yet.
  
  

Whirling Disease

• Fungi are often the cause of disease as well. Whirling disease affects the internal organs of the fish. Once infected, the fish will begin to have a curve to its spine, the skin will change shades of color becoming either darker or lighter and ulcers will appear along the body. Often times, the fish will begin to swim erratically. Since this disease is internal, like wasting disease, once symptoms show, it is usually too late. The best course of action is to remove a fish you suspect has whirling disease and isolate it in a separate tank to prevent further contamination to other fish.
  
  

Marine Ich

• This is one of the most common problems saltwater aquarium owners experience. Marine ich is caused by parasites that cause white spots to form on the fish's body which cause it to itch. It is common to see an infected fish rubbing against things in the aquarium. As the disease progresses, the fish will have trouble breathing, its fins may begin to fray or it may refuse to eat. Use a commercial treatment, found at pet stores, to treat the disease. These often contain copper to kill the parasites.