Either nipping can cause fin loss by other fish in the tank, or an injury inflicted by a sharp or rough object in the tank. Minor damage is not a problem because the guppy can grow its fin. However, a severe injury should be treated immediately because the guppy could die from a bacterial infection. So, how do you tell the difference between a fin rot and nipping?

Nipping occurs when fish bite each other while competing for food, showing dominance, mating, or defending their territory. Fin rot is caused by bacterial or fungal infections. Bacterial fin rot causes ragged rotting, while fungal fin rot causes even fin rot, with a white film on the edges.

Sometimes the two infections can appear together. Nipping isn’t concerning but can cause fin rot if the wound is too deep or if bacteria infect it.

Signs of guppy fin rot

Symptoms of fin rot will differ depending on whether bacterial or fungal infections cause the disease. The symptoms will also differ depending on the stage of the infection as follows:

Mild Fin Rot

It will be easy to treat if you are keen enough to spot the disease at a mild level. At the mild level, the rot will be at the edge of the fin. Here are the symptoms to look out for:

  1. The edge of the fin will appear tattered. You can confuse this with nipping.
  2. The tips will also start to change color. They may appear brown, grey, white, or dark.
  3. The tips could also be red and sore.

Major Fin Rot

The signs of major fin rot include the following:

  1. A major part of the fin will be rotten.
  2. Discoloration of the remaining fin. 
  3. White fuzz on the fin in case of fungal infection. 
  4. Some parts of the fin might fall off.

Body Rot

Body rot, also called severe rot, is the last stage of fin rot. At this point, you can do little to treat the guppy. However, body rot does not occur overnight, and you will have neglected the guppy to get to this point.

The symptoms of severe fin rot include the following:

  1. The fin will have rotten completely.
  2. The body may also have started to rot. 
  3. White fuzz on the base of the fin in case of fungal infection.
  4. The guppy will be lethargic.
  5. Loss of appetite.

Other causes of fin rot

Apart from nipping, fin rot can also be caused by the following:

1. Poor water conditions 

Guppies should be kept in a tank with clean water and the right water parameters. They require a temperature between 72 – 84°F and a pH of 6.8 – 7.5. 

Decayed leftovers and fish waste will result in ammonia buildup. Ammonia is toxic to fish as it will suppress their immune system, making them vulnerable to attack by bacteria. Fluctuations in the temperature and pH will worsen ammonia levels. 

2. Stress

Guppies can be stressed in a crowded tank, in poor water conditions, or with aggressive tank mates. Stress causes a weak immune system making them vulnerable to attack by diseases such as fin rot.

3. Poor diet

When guppies are fed inadequate food or food without nutritional value, their bodies weaken. They cannot fight diseases and infections or grow their fins back when injured.

4. Injuries

Guppies can get injured when other fish nip their fins or when injured by rough or sharp objects in the tank, such as stones and ornaments. If the injury is minor, the guppy can be able to grow back the fin, but for a severe injury, you will have to intervene.

When bacteria infect the injury, it can cause fin rot. 

How to treat guppy fin rot

Treatment of fin rot will depend on the severity of the infection. You first need to identify the cause of the fin rot. Fish rot is contagious and can affect other fish within the tank if left untreated.

Treat fin rot as follows:

  1. Move the affected guppy to a quarantine tank.
  2. For mild fin rot, use aquarium salt. You will need to conduct a 100% water change, then add aquarium salt. You will have to change the water daily before adding the aquarium salt. The quantity of salt to use and the days to use are indicated on the package.
  3. For major and severe fin rot, you will have to use medication. Consult a veterinary doctor for the right drug and dosage.

Minor damage on the fins is usually not a problem because the guppy can grow its fin back. However, a severe injury should be treated immediately before the wound gets infected. Fin rot affects not only guppies but all fish with long, flowing tails.

Therefore, after spotting a fish with the disease in the tank, it is important to treat it immediately so that it does not affect the other fish. Besides stopping your guppies from nipping, the affected fish should always be moved into a separate tank to avoid further injuries.

How to tell if fin rot has been cured

It will take several days to weeks for the infection to heal, depending on its severity. However, within a few days, you should be able to tell if the fish is improving.

  1. The fin rot should have stopped.
  2. Regrowth of fins, especially for mild fin rot.
  3. Open wounds should dry.
  4. Fish appetite and energy should return.


Nipping guppies are dangerous because they can cause injuries resulting in fin rot when infected with bacteria. Fin rot can also be caused by poor water quality, stress, and a poor diet.

Treatment of fish rot is determined by the severity of the infection, as a mild infection can be treated by improving the water quality and using aquarium salt. However, severe infection will require medication.

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