Quick referenceNeon Tetra Disease (NTD) is a microsporidian parasite that causes white patches and crooked spines in tetras. Untreatable in most cases; cull infected fish to prevent spread.
Symptoms
Pale patches under skin
Crooked spine
Difficulty swimming
Color fade
Restless swimming
Weight loss / sunken belly
Cause
Pleistophora hyphessobryconis spores. Spread via infected fish, eaten dead fish, or contaminated tubifex worms. Despite the name, also affects rummynose tetras, glowlight tetras, cardinal tetras, and rasboras.
Treatment options
No effective cure. No medication reliably treats microsporidia in fish. Most fish die within 3-6 weeks of symptom onset.
Cull infected fish. Most humane response. Use clove oil overdose (10 drops per quart). Burn or bury bodies; do not flush.
Salt + clean water (palliative). Aquarium salt 1 tsp/gal can ease secondary infections in early-stage fish. Will not cure NTD itself.
Sterilize tank (terminal). If outbreak is severe: euthanize all stock, drain tank, disinfect with 10% bleach 24h, rinse 3x. Restart cycle.
Always treat in a separate quarantine or hospital tank. Most medications are toxic to coral, invertebrates, and live rock biology. Consult an aquatic veterinarian for valuable fish.
Prevention
Quarantine new tetras 21 days minimum - watch for early symptoms. Avoid feeding live tubifex worms (common vector). Do not skip QT for "just a few" fish.
Fatality + outcome
Very high - 70-90% of infected fish die. Spreads through the tank in 4-8 weeks if not contained.