FRESHWATER disease

Neon Tetra Disease (Pleistophora hyphessobryconis)

Reviewed by the Fast Aquatics husbandry team · Updated May 2026

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.

Full disease database · Symptom matcher · Q&A library · Glossary · QT timeline calculator

Aquarium-keeping fundamentals

Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.

Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.

Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.

Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.

Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.

Frequently asked questions

How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.

What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.

How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.

Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.