Paragraph:Neon Tetra Disease is a set of bacterial infections caused by a Microsporidian parasite that is normally seen infecting neon tetras, but they can infect a wide variety of different species. It is more common than many realize due to some fish being only carries of the disease, or other fish being infected (but due to their size it can appear later than it normally would in smaller fish). Sadly, most if not all of the disease's signs are shown only a few days before death since this is known as a degenerative disease (it starts off slowly and then progressively gets severe rapidly). Neon tetra disease is not treatable, highly contagious to tetras, cichlids, danois, goldfish, and others inside of the aquarium. It is fatal regardless of treatment during any stages of the infection, with other bacteria being able to give the same symptoms and coloration changes that are fully treatable but not caused due to this parasite.
The early stages of infection of this disease will show no symptoms or will show very small symptoms such as not eating fully, being less active than their tank mates, and staying on the outside border of their shoal. As the disease progresses, more symptoms will appear including lack of eating, the fish's color may fade (if the fish is a neon tetra the color between their tail and body will turn an off white or gray color while their blue fades), the fish may have trouble swimming around, and lastly, the shoal of fish will appear to have "kicked out" the infected fish from their group. Whenever a shoaling or schooling fish is sick, the rest of its species members will remove the infected fish from their group to protect them from getting the sickness as well (hence why seeing a lone fish that should be in a group hang out by itself is normally a bad sign to start with).
Pleisotphora hyphessobryconis is the parasite that is the cause of the neon tetra disease and allows for secondary bacterial infections to also infect the fish. The parasite enters the fish's body by being accidental ingested either through a food source, if the fish eats another infected fish's poop, or if there are any nips that the fish may take to other tank mates who are infected. Once the parasite enters the body it starts to produce a highly large number of spores that can infect other fish by the same accidental ingestion. However as this parasite makes its way into the organs, it will also release spores into the fish's digestive tract that can infect other fish if they are inside of the tank water column. The loss of color that can be see in neon tetras is due to the parasite eating the fish from the inside out, where damaged tissue can be seen which is a common trait of color loss (especially on a highly reflective fish such as neon tetras and cardinal tetras).
Treatment and Medication
With no known cure to this parasite, many have stated that using a bacterial and fungus medication does slow down and can prevent death if given in the early stages. No known documented proof such medicines do truly work, and that if they did work if the disease was correctly diagnosed (as there are many that can show similar symptoms but are not neon tetra disease). The only way to make sure that you do not get any fish that have this disease is to always buy from a store that is not only reputable, has not had any fish die showing the symptoms listed above, but mainly only gets new fish from trusted and well-known breeders.
Due to the way that this disease affects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected or learn about what possible other diseases they might have.