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Understanding and Treating Neon Tetra Disease

Neon tetra disease was first discovered in neon tetras, hence the name. And while it’s most common in neon tetras, in actuality, other fish can be susceptible to this disease as well. The bad news is neon tetra disease is a nasty ailment with high fatalities. The good news is it’s preventable.

So, what is it about neon tetras that makes them suspectable to this disease? Is there anything that you can do to prevent it from occurring in your aquarium? 

Learn more about the disease and how to prevent it below. 

What is Neon Tetra Disease?

Neon tetra disease is caused by a parasitic protozoan known as Pleistophora hyphessobrycoins, belonging to the Microsporidia family, which is a particularly dangerous family of parasites. 

These parasites have a complex life cycle, which includes the production of resistant and infectious spores. Fish become infected when they either eat food items that contain the spores, or eat the dead bodies of other fish (which some fish species do). The spores hatch inside the fish, and the parasite starts to consume the inside of the fish. Throughout its life cycle, this parasite remains inside the fish, except for during the spore’s stage.

🐠 Give your neon tetra a long, happy life by understanding its lifespan and factors that affect it.

Neon tetra disease is degenerative in nature. This means it starts off slowly but becomes more severe with time. The parasite eats away at the fish, starting with the stomach and digestive tract. It then works its way to the other organs, muscles, gills, and skin. This disease can lead to secondary infections, which is also what makes it particularly dangerous.

Impact on Other Aquarium Fish Species

Neon tetra disease gets its name because it was first identified in neon tetras. However, other members of the tetra family are also vulnerable to this disease. Neon tetra disease has also been found in cichlids, rasboras, barbs, and danios.

Surprisingly, the cardinal tetras appear to be largely immune to neon tetra disease;  however, cardinal tetras are susceptible to a disease known as dermocystidium. 

Cardinal tetras that are inflicted with dermocystidium will develop blisters on their body. Unlike neon tetra disease, dermocystidium is caused by a fungus. Like neon tetra disease, however, dermocystidium is incurable.

What Are Symptoms of Neon Tetra Disease

Neon tetra disease has characteristic symptoms that follow a pattern as the parasitic infection progresses. The symptoms appear in the following order:


In the early stages of neon tetra disease, the fish will become restless, especially at night. The sick fish will not engage in schooling behavior, and its swimming may become erratic.


The infected fish will withdraw from the school and hide. This reclusive behavior is the result of them being drained of energy by the disease.  Instead of seeking safety through schooling, they’ll hide behind plants, rocks, or decorations.


With the progression of the disease, the parasite will start to affect the muscle tissue. This may cause the muscle tissue to become white in color.

The discoloration normally begins along the spine area and as destruction of the muscle tissue progresses, the discoloration will spread along with it.

White Cysts

As the parasite infects the muscles, white-colored cysts will form on the muscles giving the fish a lumpy appearance.

Swimming Difficulties

The damage to the muscles caused by the parasite leads to muscle damage and spine curvature, resulting in the fish having difficulties swimming.

Secondary Infections

Neon tetra disease can often lead to secondary infections, including bloating and fin rot.

A Diagnostic Challenge

Neon tetra disease is often misdiagnosed as there are other diseases that can share similar symptoms.  One of those diseases is false neon tetra disease, which is caused by a bacterium, not a parasite.

False neon tetra disease is also less severe than neon tetra disease, and it can be treated. Unfortunately, it’s difficult to distinguish between these two tetra diseases. For this reason, you have nothing to lose by quarantining the affected fish and treating it with antibacterial medication.

Causes of Neon Tetra Disease

Neon tetras come from the river systems of northern South America like the Orinoco and Rio Negro rivers. These waters are dark-colored, and acidic. Because of their acidic nature, the rivers are low in bacteria count. And since neon tetras’ immune systems don’t have to contend with bacteria, they’re not highly developed.

The neon tetras that you purchase at your local tropical fish store are likely farm-raised and sold to wholesalers, who purchase large batches of them at a time. Keeping fish crowded together increases the bacteria count, which the neon tetra’s immune system can’t handle.  

This is why neon tetra disease was first observed in neon tetras—because these fish were placed in environments that their immune systems couldn’t handle.

There are only two ways that neon tetra disease can make its way into your aquarium:

  1. You purchased a fish that already was infected by the parasite.
  2. Your neon became infected in your aquarium because of the water quality (including food contamination).

How Do You Treat Neon Tetra Disease?

Neon tetra disease is fatal, and there’s no cure for it. It’s a slow-killing disease, and it can take weeks or even months before the fish finally dies.  Many aquarists euthanize their fish to end their suffering.

Neon tetra disease is also highly contagious. Though there’s no cure for it, there are procedures that you need to take to prevent it from spreading.

How Do You Treat Neon Tetra Disease?

There is no treatment for neon tetra disease. If you suspect that one of your fish has neon tetra disease, you need to quarantine it and any other fish that appear to be affected. Remove the unaffected fish and give the  aquarium a thorough cleaning by doing the following:

  1. Mix a solution of one part bleach to eight parts of water.
  2. Use the solution to spray the aquarium and any equipment or decorations that it may contain and let them sit for 20 minutes.
  3. Give the aquarium and its accessories a thorough rinsing, and let the aquarium and accessories air dry for a full day.
  4. Fill the aquarium with de-chlorinated water and let it sit for several hours.
  5. Empty the aquarium, refill it with de-chlorinated water, and let the aquarium complete its nitrogen cycle.
  6. Add the unaffected fish when the aquarium has completely cycled.

🐠 Learn more about nitrogen cycling your aquarium to make it safe for its inhabitants.

Does neon tetra disease go away?

Unfortunately, neon tetra disease does not go away. The parasite continues to eat away at the fish’s body until it dies.

Neon Tetra Disease Prevention

The following are preventative measures that you can take to prevent neon tetra disease from making its way into your aquarium:

Be Selective

Be selective when purchasing your neon tetras.  Your neon tetras should look healthy, have vibrant colors, and be schooling with the other tetras.


It’s important that you quarantine all new fish before adding them to a community tank. I recommend that you quarantine new fish for at least two weeks to determine if they have any diseases.

Avoid Live Food

Live food can contain neon tetra disease and other parasites. For this reason, I recommend that you feed flake or freeze-dried foods. If you must feed live food, purchase it only from a reputable tropical fish store.

🐠Here’s a full guide on what neon tetras eat and what to feed them.

Maintain Water Quality

Pleistophora hyphessobryconis thrives in waters that have:

  • Warm temperatures
  • Low pH
  • Low levels of oxygen
  • High levels of organic matter

Based on this information, the best way to prevent neon tetra disease is to create an environment that’s the opposite of the aforementioned.  

Choose the Right Filters

Neon tetras need water that’s clear, well-filtered, and is rich in oxygen. This can be achieved by adding air stones or a sponge filter. For these reasons, neon tetras do best when they are introduced to a mature aquarium where the filter and substrate haven’t been cleaned for several months.  

Back-hanging filters don’t provide adequate biofiltration for neon tetras.  If you have a back-hanging filter, I recommend that you supplement it with one of the following:

  • Under-gravel filter
  • Canister filter that contains an effective media such as foam static K1.
  • A sump if you have a large aquarium.

The back filters alone won’t keep up the water quality that’s needed by neon tetras. Any of the three filter options previously mentioned can stand alone.

Also, don’t clean your filter media unless there’s a noticeable reduction in the water flow. The reason for this is that the filter media provides a place for beneficial bacteria to grow.  These bacteria will help you maintain the proper water quality.

🐠View our full guide on fish tank filters and how to choose the best one. 

Weekly Tank Cleaning

Purchase an aquarium vacuum gravel cleaner. They are inexpensive and can be found in most tropical fish stores.  Once a week, siphon the substrate for any leftover food or other organic materials that may have been collected.

Partial Water Changes

Do a partial water change weekly where you change 20% of the aquarium. When doing a partial water change, make sure the water you use to replace the old water has the same water parameters as the old water.

The temperature, pH, and water hardness of the new water should be the same as the old water.  Also, make sure to add water conditioner to the new water to remove any chlorine that may be in it.

Do Regular Water Tests

Test the water on a regular basis using a water testing kit, which can be purchased at most tropical fish stores. The water parameters for neon tetras should be as follows:

  • Ammonia and nitrite levels = 0 ppm.
  • Nitrates= 10 ppm or less.
  • pH= 6.5-7.5
  • Water hardness= 1-2 dKH.
  • Temperature: 70-75 degrees Fahrenheit (21-24 degrees Celsius).

Purchase UV Sterilizers

Your aquarium filter isn’t able to kill bacteria; it can only help control their growth. To kill microorganisms, you can purchase a UV sterilizer. UV sterilizers are inexpensive and can help assure that Pleistophora hyphessobryconis and other harmful microorganisms do not survive in your tank.

Your neon tetras deserve a long, happy life

We hope that you enjoyed this article. Neon tetra disease can be a nightmare for an aquarist. However, this disease is preventable. Learn about the conditions that neon tetras experience in the wild and replicate them in your aquarium. If you do this, you should not have to worry about neon tetra disease making its way into your aquarium.  Please share your comments and share this article.

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