Like most pets you have they will sometimes get diseases and fish will too. So fishes should be checked often for diseases and odd behavior from fish. To prevent the spread of diseases in your aquarium setup a quarantine aquarium and place the affected fish in the aquarium and treat it with medication. Here's a list and information about common fish diseases.
Ick- Ick or Ichtyopthirius is the most common disease found in an Aquarium with inhabitants. Ick is white spots that attach themselves on to fish. Ick will cause discomfort and pain to the fish. Ick is a contagious disease that will reproduce and affect other fish in the aquarium. Ick can be caused by stressful factors like poor water conditions. There are many medications in pet stores today and many can cure ick quickly.
Common Fungus- There many kinds of Fungus diseases. Most fungus are cotton wool like stuff growing on the fish. There are many different treatment out there and aquarium salt may work too on fungus but we recommend the medication treatment.
Fin Rot- If your fish gets injured check the wounded fish more often because fin rot is caused by bacteria entering a wound. Fin Rot is also caused by poor water conditions. Fungus development on the fish is common. Water Changes and medication is one way to cure Fin rot.
Dropsy- Dropsy is disease caused viral or internal kidney infections. Fluids build up in the body cavities and it creates pressure in the body and it becomes swollen. Pop eye is another symptom for Dropsy. Cure is rarely successful but there are now some medication that would cure dropsy .