Symptoms
Color fading — bright neon dimming to pale.
Body curvature — fish swims at angle, eventually unable to right itself.
Wasting — visible weight loss despite eating.
Erratic swimming — separating from school.
Cause
Pleistophora hyphessobryconis — internal parasite. Spreads via consumption of dead infected fish.
No effective treatment exists. Kill all symptomatic fish before they die naturally.
Tank Decontamination
Remove all infected fish immediately. Bleach all décor 1:10, rinse extensively.
Skip new tetra introduction for 6 months minimum after outbreak.
Prevention
Quarantine new neons 30+ days. Watch for early signs.
Buy from established breeders — wild-caught and pet shop neons highest risk.