NEON TETRA DISEASE
In neon tetras a disease sometimes occurs in which some blemish or spot is formed in the blue-green line, which will gradually extend over a larger area and grow into a light-colored band, which shows generally prependicular to the longitudinal axis of the body. The initial spot may appear anywhere in the course of the line.
Although the disease was first ovserved in neon tetras, Hyphessobrycon innesi, it is not confined to this species only....(blah blah blah)
...Upon microscopic examination of thin sections from the region of the pathological band it may be observed that its cells are necrotic, that it, the tissues consist of dead and dying cells
The disease seems to be due to an infection with sporozoans belonging to the genus Plistophora. These have also been found in swordtails.
TREATMENT
Methods for prevention and cure are still unknown. *It has been claimed that a cure could be effected with a rather strong dosage of Methylene Blue (medical quality), namely 1 gram in 100 liters or 5.7 grams per gallon*. In experiments by other investigators Methylene Blue failed to cure the disease (duh)