While its name may suggest so, the neon tetra disease is not restricted to the neon tetra (Paracheirodon innesi) species alone. It is not restricted to the tetra family either, though it is much more common in the members of this family. Species like cichlids, angelfish, rasboras, goldfish, barbs, etc., are also vulnerable to it. This disease is a serious threat as it spreads rapidly, is incurable, and can be fatal for the fish.
The disease is caused by a sporozoan called Pleistophora hyphessobryconis, a parasitic spore-forming protozoan that reproduces through spores. Infected or contaminated neon tetra food, like the bodies of the dead fish or live food like tubifex, serves as intermediate host for these parasites, which enter the fish in the form of spores.
When they reach the intestinal tract of the fish, the freshly hatched embryos burrow through the intestinal wall and develop cysts inside the muscle tissue. As a result, the muscles holding the cysts begin to die, and the necrotic or mortified tissue becomes pale, eventually turning white in color.
Once the cyst reaches the aquarium water, it breaks open and releases the spores, as a result of which the other fish in the water get infected. Apart from this, if the host fish has infected kidneys, the spores can also be ejected into the tank through its waste. In either case, the disease spreads rapidly and causes several fish to die.
The first symptom that you may see in the infected fish is that it will no longer school with other fish and will be very restless, especially at night. As the disease progresses, its swimming will become very erratic and the affected muscle tissues will turn dull and white. Eventually, the pale coloration will expand and become more dominant in the areas along the spine. Due to muscle damage, you will notice spine curvature or deformation, which will make it difficult for the fish to swim. Rotting of fins, lumpy appearance, and bloating are other symptoms that can also be seen in a fish suffering from this disease.
As said before, the disease is incurable. So, once affected, it slowly kills the fish. There are certain species, such as the angelfish, that may survive for some time, but death is inevitable. Though the disease cannot be treated, its spread can be prevented by resorting to certain precautionary measures, like quarantining or isolating the new fish for two weeks, maintaining high water quality, and not purchasing fish from a tank having ill or dead fish. These preventive measures can reduce the risk of neon tetra disease by a great extent.
If you notice any of the symptoms of this disease in your fish, you should isolate it. This will keep the infection from spreading and harming other fish in the tank.