Fish Care

Fin rot in fish – causes, symptoms, treatment and prevention

fin rot
What is the fin rot?

Fin rot is a common disease that describes the rot or decay of the fins or tail of a fish, this is caused by bacteria that eats your fish’s fins. These illnesses are easy to treat but can lead to other serious problems – it can rot the whole fish’s body and cause death If left untreated.

Fin rot is not caused by a single type of harmful bacteria, especially waterborne bacteria. There are many other types of bacteria that can lead to fin rot such as; fungal and pseudomonas fluorescens. Sometimes, both types of infections are seen together. Most times bacteria are harmless as long as your aquarium is cleaned regularly.

Fin rot starts at the fins edge, and then destroys more tissue until it reaches the base. When it reaches the base, the fish will never be able to regenerate lost tissue. At this point, the disease can begin to invade the body of the fish; this is called advanced fin and body decay.

Fin Rot Symptoms in Aquarium Fish

Fin rot is commonly found in aquarium fish such as goldfish and betta fish. Symptoms may vary depending on how long the fish has been affected:

  • In the first stage of the fin rot, the fins and / or tail begin to show a change in color, especially at the edges. Depending on the color of the fish, the color may change to white, red, or black.
  • As the infection spreads, small fragments of the fins die and begin to fall off, leaving a stunted edge.
  • Over time the fins become smaller and shorter as dead flesh continues to remove the affected fins. The entire fin and / or tail is rotten, and infection begins to invade the body, which can lead to loss of life.
What are the causes of fin rot?

The most common causes of final rot are poor water quality and improperly low temperatures or exposure to other potentially infectious fish. Aggressive tank mates that are larger or known for nipping, the stress from this nipping by other fishes can lead to injuries which are also common reasons for fin rot.

Overcrowding, over-feeding, and transporting or handling can also create stress that can lead to fin rot.

These symptoms are often accompanied by loss of appetite, less activity, and your fish sitting at the bottom of the tank.

How to treat fin rot in your fish:
  • Clean the gravel at the bottom of the aquarium to remove any debris and waste.
  • Make a 25% water change for your fish tank
  • Check and monitor your water conditions. Check factors such as pH, temperature, chlorine, ammonia, nitrite and nitrate levels.
  • For the water temperature, make sure it is appropriate for your species of fishes Make sure there is no chlorine, ammonia, or nitrite in the water and the nitrate is less than 40 ppm (mg / L).
  • Move the affected fish to a separate tank, especially the ones that show signs of fin rot. This is important in preventing further decay from spreading to other fish. It is also a good idea to move the fish when they are being harassed by aggressive tank mates to prevent further nipping.
  • The following medicines will help to treat the disease. Melafix, Methylene Blue, and Furan-2 Powder. It is also recommended that you consult your veterinarian (there are many Certified Aquatic Veterinarians now) to find the right antibiotics for your fish.
  • Always treat according to the instructions of the veterinarian, as different dosage preparations may vary from manufacturer to manufacturer. It is very important to continue treatment for the recommended duration, as sooner termination of treatment may lead to a recurrence of the infection.
  • Monitor your fish daily to check for progress. If treatment is successful, you may notice that the damaged fins and tail will grow back a few weeks later.

It is important to treat your fish as soon as possible to prevent further rot and harm to your fish. If caught early, the final rot can be treated, and your fish fins will grow slowly with care and time. In the most severe cases when the final decay has reached the fish’s body, the tissues will not be regenerated.

Several antibiotics are effective in treating chronic inflammation, but the root cause must be addressed to ensure that the disease does not re-occur.

How to Prevent Fin Rot
  • The best way to prevent fin rot and other fish diseases, is good aquarium care; good water quality, maintaining adequate water temperature and regular water changes.
  • Do not overload the tank, and look for signs of fighting between fishes that may nip at each other. Although the fish are quiet and peaceful to watch, not all fish are harmonious. It is also advisable to monitor your fishes and check if they are compatible to prevent any fighting between them.
  • Avoid over feeding, only feed the fish as much food as it will eat for about three minutes, twice a day. Overfeeding is the most common mistake made by all fish owners, and contributes to the poor water quality that builds up bacteria. Feeding time is also a good time to take a closer look at the behavior of your fish. Keep an eye on the daily routine for any changes in their fins, tail, body, behavior, and appetite.


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