This disease was originally described in Neon Tetras, but can affect many other species of fish. In Neons, one of the early signs of this disease is a loss of the red colour, and difficulty swimming Note that there is a so-called "false neon disease", which is bacterial, and shows very similar symptoms. It is impossible for the home aquarist to determine for certain the difference between NTD and false NTD on the basis of visible symptoms alone, without laboratory backup. This disease has also been confused with Columnaris.

False NTD: The loss of the blue colour and pale skin patches.

The disease is caused by a microsporidian parasite. The disease is most likely to be passed on from newly acquired fish, which have not been quarantined.

These parasites are very resistant to medications, and there are no proven effective treatments. Some anti-parasite medications claim to treat this disease, but there effectiveness is debatable. Some apparent 'cures' may have been the result of successful treatment of false-NTD. The best course of action is to isolate sick fish quickly, and maintain good water quality to reduce the chances of more fish succumbing to the disease. The use of a diatom filter, which can reduce the number of free parasites in the water, may help.