The symptoms of fin rot in goldfish include torn-looking, ragged tails and fins that appear to have been eaten away. As time progresses, the tail and fins diminish. Fin rot is caused by a stress on the fish, such as poor water quality or injury. Bacteria that naturally occur in the water can then attack the edges of the fins. In advanced cases, a white fungus can grow on the edges of the fins as well. Fortunately, fin rot is treatable. If you start treatment as soon as you notice the fin rot, you can expect full recovery for your goldfish.
Change the water in your goldfish bowl or aquarium. Scrub down the sides to get rid of algae and other growths. A major water change improves the pH and other water quality factors in the goldfish's environment and gets rid of much of the bacteria that grows because of fish waste in the water.
Mix in 1 tbsp aquarium salt for every 5 gallons of water before returning the fish to the bowl or aquarium. Stir the mixture until it dissolves. Aquarium salt eliminates many common bacteria from the water. Do not use table salt. Do not add any salt at all if you have live aquarium plants or fish that do not tolerate salt well, such as Corydoras catfish.
Add medication designed to remedy fin rot to the water. Consult your local aquarium store staff for advice and read labels carefully. Common fin rot medications include tetracycline, chloramphenicol and furance. Follow package directions exactly when adding the medication to the water.
Observe the infected goldfish closely for signs of improvement. Monitor the water quality and keep the fish bowl or aquarium water at a high standard of cleanliness at all times to prevent further fin rot infections.
Do not use goldfish fin rot cure for other fish. They may not tolerate the treatment well.