Neon Tetra Fin Rot: Causes, Symptoms & Prevention

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Neon tetras are highly admired as community fish due to their peaceful nature and resilient characteristics.

Additionally, their brightly colored and flowing tails create a calming spectacle as they gracefully move within the aquarium.

Unfortunately, these beautiful fins and tails are prone to a condition known as neon tetra fin rot.

So, what exactly is neon tetra fin rot? What causes it? And are there any measures to prevent or manage it?

In this article, I will answer these questions as thoroughly as I can.

What Is Neon Tetra Fin Rot?

Fin rot in neon tetras is a common disease often triggered by stress and poor water conditions.

The deterioration of the fish’s fins can be triggered by many types of bacteria, including Pseudomonas fluorescens and Aeromonas, or even fungal infections.

The infection usually starts at the fin edges, causing them to appear ragged, turn black or brown, or even develop white dots.

The fins may fray or even fall off in severe cases.

If untreated and the rot reaches the fin base, the neon tetra will lose its ability to regenerate the lost tissue, and the disease might progress to attack the fish’s body, an advanced stage known as fin and body rot.

Neon Tetra Fin Rot Causes

1. Fin Injuries

Neon tetras are small and have delicate fins. Any physical injury to the fins can trigger fin rot. 

This can occur due to fights with other fish, accidents with tank decorations or equipment, or even through rough handling during netting and transportation.

An injury to a fin creates an open wound, which can easily get infected by bacteria present in the water, leading to fin rot.

2. Poor Water Quality

Neon tetras thrive in clean, well-maintained water. Poor water quality is a significant cause of fin rot.

If the water is dirty, contains high levels of nitrates or ammonia, or the pH is not suitable for tetras, it can lead to fin rot.

These conditions weaken the fish’s immune system, making it easier for bacteria to invade and cause infections like fin rot.

Regular water changes and proper tank maintenance can help prevent this.

Also Read: 17 Neon Tetra Diseases & Their Treatments

3. Fluctuating Water Conditions

Neon tetras prefer stable water conditions.

Rapid changes in temperature, pH, hardness, or other water parameters can stress the fish, lowering their immune response and making them more susceptible to infections like fin rot. 

It’s crucial to maintain a stable environment in your aquarium, with consistent water parameters suitable for neon tetras.

4. Stress

Stress is a significant contributor to many health problems in fish, including fin rot.

Stress can be caused by various factors, such as poor water quality, inappropriate diet, bullying by other fish, or even constant exposure to bright lights.

When a fish is stressed, its immune system weakens, making it more susceptible to infections.

Ensuring a stress-free environment, including proper diet, adequate hiding spaces, and compatible tank mates, can help in preventing fin rot.

5. Overpopulation

A crowded aquarium can lead to several problems, including the quick spread of diseases like fin rot.

Overcrowding causes stress and can degrade water quality faster due to higher waste production.

It may also lead to aggressive behavior and injuries due to lack of space, and the spread of bacteria is faster in an overpopulated tank.

Hence, maintaining an appropriate number of fish in the aquarium is important for their overall health and well-being.

Recognizing Fin Rot in Neon Tetras

Fin rot manifests in three stages: mild, major, and severe:

1. Mild Fin Rot

  • Small, irregular, or ragged edges on the fins.
  • Discoloration of the fin edges, often white or a lighter color than normal.
  • Fins may appear slightly shorter or frayed.

2. Advanced Fin Rot

  • More noticeable and widespread discoloration of the fins, often turning black or red.
  • Fins start to deteriorate significantly, appearing heavily frayed or eaten away.
  • Slight lethargy or unusual behavior may be noticeable.

3. Severe Fin Rot

  • Significant loss of fin tissue, sometimes down to the base of the fin.
  • Fins may appear red, black, or have a cotton-like growth, indicating severe bacterial infection.
  • Open sores or ulcers on the body close to the base of the fins.
  • The fish is noticeably sick, exhibiting lethargy, loss of appetite, and other signs of distress.
  • If not treated, severe fin rot can be fatal as it may lead to systemic infection.

Also Read: Neon Tetra Ich (White Spot)

Treating Neon Tetra Fin Rot

My go-to product with this condition is the API MELAFIX (link to Amazon).

The way of using it depends on the severity of your case. You may also use other products, just make sure to consult an aquatic vet beforehand:

1. Treating Mild Fin Rot in Neon Tetras

For mild cases of fin rot, you can follow these steps:

  • First, improve the water quality in your aquarium. Do a 25-50% water change, ensuring the new water matches the old water’s temperature and pH.
  • Clean your tank thoroughly, removing any waste, uneaten food, or decaying plants which can increase the levels of harmful bacteria.
  • Check the water parameters (ammonia, nitrite, nitrate, pH, etc.) and correct any imbalances.
  • Treat the water with an over-the-counter antibiotic or antibacterial medication designed for fish, following the manufacturer’s instructions carefully.
  • Isolate the affected fish if possible to prevent the spread of infection.
  • Monitor your fish daily for improvement or worsening of symptoms.

2. Treating Advanced Fin Rot In Neon Tetras

Here is how to address advanced fin rot in neon tetras:

  • Immediately change 50-75% of the aquarium water, matching the temperature and pH.
  • Use a vacuum or siphon to remove waste from the bottom of the tank.
  • Isolate the affected fish in a separate hospital tank if possible to prevent spreading the bacteria.
  • Treat the water with a stronger antibiotic or antibacterial medication suitable for fish.
  • Keep monitoring your fish closely, and do daily water changes in the hospital tank.
  • If there is no improvement, you may need to consult a fish health professional for advice on stronger treatments.

3. Treating Severe Fin Rot in Neon Tetras

Follow these steps if your neon tetra suffers from severe fin rot:

  • Immediate isolation of the affected fish is critical to prevent the spread of the disease.
  • A major water change (75-100%) may be required in the hospital tank, ensuring the water parameters are suitable for your fish.
  • Apply a broad-spectrum antibiotic treatment suitable for fish, following the manufacturer’s guidelines. You may need to consult a vet for prescription antibiotics at this stage.
  • Monitor your fish’s condition very closely, doing daily water changes and medication applications.
  • You may need to consider euthanasia if the fish’s condition continues to deteriorate, to prevent suffering. Consult a professional to make this difficult decision.
  • Thoroughly clean and disinfect the main tank to prevent the recurrence or spread of the disease.

Dealing With Fungal Fin Rot In Neon Tetras

Even though it is rarer, fin rot in neon tetras can be due to a fungal infection. Follow these steps:

  • Identify the Fungal Infection: Look for cotton-like growths on the fins and body of the neon tetras. These could be signs of a fungal infection accompanying fin rot.
  • Isolate the Affected Fish: To prevent the spread of the fungus to other fish in your tank, it’s essential to separate the sick fish into a separate, clean quarantine or hospital tank.
  • Improve Water Conditions: Perform a substantial water change (50-75%) in the main tank to remove fungal spores and improve water conditions. Maintain the temperature and pH at levels suitable for neon tetras.
  • Medication: Treat the affected fish with an antifungal medication suitable for fish, such as Methylene Blue or a specially-formulated antifungal treatment. I personally like the Mars Fishcare North Amer API Pimafix (link to Amazon).
  • Maintain the Hospital Tank: Conduct daily partial water changes in the hospital tank, about 10-20%, to help keep water conditions optimal.
  • Monitor the Fish: Keep an eye on the affected fish daily. Monitor their behavior and check if the fungal growth is diminishing.
  • Continue Treatment: Continue the antifungal treatment according to the instructions, even if the fungus appears to be gone. This helps ensure that all fungal spores are eradicated.
  • Return to Main Tank: Once the fish has fully recovered, acclimate it to the main tank’s water conditions gradually before reintroducing it.

Preventing Fin Rot in Neon Tetras

After treating your neon tetras, here is how you can prevent this condition in the future:

  • Maintain Optimal Water Conditions: Keep the temperature, pH, and hardness within the ideal range for neon tetras (temperature: 70-81°F (21-27°C), pH: 6.0-7.0, hardness: 1-2 dGH).
  • Regularly Clean The Aquarium: Remove uneaten food, decaying plant matter, and fish waste promptly. This helps prevent the growth of harmful bacteria and fungi that can cause fin rot and other diseases.
  • Perform Regular Water Changes: Change 10-20% of the water in your aquarium every week. This will help maintain water quality by diluting nitrates and other harmful substances.
  • Avoid Overcrowding: Each neon tetra needs at least one gallon of water. Overcrowding can lead to stress and increased waste, which can degrade water quality and lead to diseases like fin rot.
  • Provide Nutritious Food: A balanced diet will keep your neon tetras healthy and boost their immune system. Feed them high-quality flake food, along with occasional treats of live or frozen food.
  • Ensure Hiding Spots: Providing plenty of hiding spots will help keep your neon tetras stress-free. You can use plants, rocks, or aquarium decorations to create these spots.
  • Quarantine New Fish: New fish can carry diseases that could be transmitted to your existing fish. Quarantine new fish in a separate tank for at least two weeks and monitor them for signs of illness before introducing them to your main tank.
  • Choose Compatible Tank Mates: Neon tetras are peaceful fish and should be kept with other peaceful species. Aggressive or fin-nipping fish can cause injuries that can lead to fin rot.

When picking your neon tetra’s tank mates, I would strongly recommend against these species as they are known to exhibit aggressive behavior:

  • Angelfish (Pterophyllum scalare)
  • Betta Fish (Betta splendens)
  • Tiger Barb (Puntigrus tetrazona)
  • Cichlids (various species)
  • Silver Dollar Fish (Metynnis argenteus)
  • Arowana (Osteoglossum spp.)
  • Red-Tailed Shark (Epalzeorhynchos bicolor)

Also Read: Black Spots On Neon Tetras


Fortunately, fin rot is a treatable and preventable disease. If you suspect that your neon tetra is infected, the first step is to quarantine the fish.

Next, assess the severity of the case and adjust the treatment accordingly.

If you are unsure of what to do, always consult an aquatic veterinarian. They will guide you through the entire process.