There are a number of diseases that are common in goldfish, and capable of being contagious to other goldfish if not treated in a timely manner. Most goldfish can make a complete recovery when the proper treatment is administered. Some of the most common goldfish diseases include cotton mouth, dropsy, fin rot, flukes, ich and velvet.
Cotton mouth, capable of affecting all freshwater fish, is a bacterial infection. Symptoms in goldfish include lethargic behaviour, cottony or threadlike growth from the mouth, dry skin or a thick and heavy slime coat. Treatment options for cotton mouth include medicated food, antibacterial injection or Melafix, which is commercially available. You can prevent this syndrome by maintaining water quality and reducing the level of organic debris in the tank.
Dropsy, a common viral or bacterial infection, is caused by stress or poor tank conditions. Symptoms of dropsy may include swollen body, scales sticking out, ulcers on the body, refusal to eat and protruding eyes. Difficult to treat, dropsy mortality rate in goldfish is quite high. Treatment involves broad-spectrum antibiotics, salt solutions added to the water, medicated food and maintaining a tank temperature of between 25.6 and 26.7 degrees Celsius.
Flukes--including gill flukes and body flukes--are a common parasite that goldfish can contract. Symptoms include isolated, scratching, clamped fins, excessive slime coat and flashing. Goldfish may also develop ulcers and sores from the scratching. Common treatment options for flukes include Quick Cure, Formalin, Healthguard, Fluketabs, Droncit and Potassium Permanganate (PP). Repeated treatments may be necessary to wipe out newly hatched flukes if eggs and larvae were present in the tank.
Ich, also referred to as white-spot, is a common disease that affects goldfish and other freshwater fish varieties. Ich is simple to detect as it causes white spots to form all over the body and fins of the fish. If one fish has developed ich, then the entire tank will need to be treated using a .3 per cent saltwater solution and copper, formalin or malachite green, all of which are commercially available treatment options. Continue treatment for at least six days and change out the substrate to remove remaining parasites from the tank.
Velvet, a disease caused by the presence of the parasite Oödinium, is capable of taking over an entire aquarium just like ich can. Its symptoms include scratching, flashing and white to yellow patches on the skin. Treat velvet with a medication that contains Formalin for at least three days. You can help prevent this disease by quarantining new additions to the tank before they are added into the environment.