Neon Tetra Disease

Pleistophora hyphessobryconis or Neon Tetra Diease, a Protozoan

Paracheirodon innesi - Neon Tetra
Neon Tetra. Kai Schreiber


  • Names: Neon Tetra Disease, Pleistophora
  • Disease Type: Protozoan
  • Cause / Organism: Pleistophora hyphessobryconis


Neon Tetra disease is more common than many aquarium enthusiasts realize, and affects species beyond neon tetras. Named after the fish that it was first identified in, the disease strikes members of the tetra family most often. However, other popular families of aquarium fish are not immune.

Cichlids such as Angelfish, and Cyprinids such as Rasboras and Barbs, also fall victim to the disease. Even the common Goldfish can become infected. Interestingly enough, Cardinal tetras are resistant to the ravages of Neon Tetra disease. Caused by the sporozoan, Pleistophora hyphessobryconis, the disease is known for its rapid and high mortality rate among neons. To date there is no known cure, the only 'treatment' being the immediate removal of diseased fish to preserve the remaining fish.

The disease cycle begins when parasitic spores enter the fish after it consumes infected material, such as the bodies of dead fish, or live food such as tubifex, which may serve as intermediate hosts.

Once in the intestinal tract, the newly hatched embryos burrow through the intestinal wall and produce cysts within the muscle tissue. Muscles bearing the cysts begin to die, and the necrotic tissue becomes pale, eventually turning white in color.


  • Restlessness
  • Fish begins to lose coloration
  • As cysts develop, body may become lumpy
  • Fish has difficulty swimming
  • In advanced cases spine may become curved
  • Secondary infections such as fin rot and bloating

During the initial stages, the only symptom may be restlessness, particularly at night. Often the first thing an owner will notice is that the affected fish no longer school with the others.

Eventually swimming becomes more erratic, and it becomes quite obvious that the fish is not well.

As the disease progresses, affected muscle tissue begins to turn white, generally starting within the color band and areas along the spine. As additional muscle tissue is affected, the pale coloration expands. Damage to the muscles can cause curvature or deformation of the spine, which may cause the fish to have difficulty in swimming. It is not unusual for the body of the fish to have a lumpy appearance as the cysts deform the muscles.

Rotting of the fins, especially the caudal fin, is not uncommon. However, this is due to secondary infection rather than a direct result of the disease itself. Bloating is another secondary infection.


  • None, separate or euthanize diseased fish

There is no known cure. To ensure all fish are not lost, remove diseased fish from the tank. Some species, such as Angelfish, may live for quite some time. However, they should be separated from uninfected fish to avoid spreading the disease.


  • Quarantine new fish for two weeks
  • Maintain high water quality
  • Do not purchase from a tank with ill fish

The best prevention is to avoid purchasing sick fish, and to maintain high water.

Carefully observe the suppliers fish. Do not purchase any fish from tanks where there are sick, dying, or dead fish present. Fish that do not school, or hang apart from the others, should be suspect.

Common Questions
Q: I've heard that just like ich, all neon tetras carry this disease.
A: Not all neons are not carriers, however if the disease is present in one specimen in a tank, it may have already infected all other neons in that tank. Never purchase a fish from a tank where other fish appear to be sick.

Q: Does Erythromycin cure this disease? How about Nalidixic Acid, or Protozin?
A: There is no known cure for Neon Tetra disease. Erythromycin is primarily effective against gram-positive bacteria, and no evidence exists that it has any effect on Neon Tetra disease. Some owners have reported success in alleviating symptoms of the disease by using Nalidixic Acid, which is generally used to treat gram-negative organisms.

However, this has not been substantiated in scientific studies. Protozoan drugs such as Protozin, have also been reported to have relieved symptoms of the disease. However, as with other treatments, an actual cure has not been scientifically documented.

Many of the reported cures are the result of misdiagnosis. Certain bacterial infections mimic the symptoms of Neon Tetra disease. Those diseases often respond to medication, thus giving rise to the incorrect belief that there is a cure for Neon Tetra disease.

Q: Once a tank has Neon Tetra disease present, it can never be eliminated from that tank.
A: Because consuming infected material passes on the protozoa, it is nearly impossible to rid a tank of the parasite if there are infected fish present. Anytime one fish picks at another, they are at risk of contracting the disease. For this reason, it's imperative to quarantine infected fish. It is true that the spores may present in many aquariums, however careful cleaning and maintenance will remove most of them. It is only when a fish consumes the spores that they become infected.