Discus with white feces: step-by-step Hexamita treatment

In short

• Normal feces: brown, compact, short (1–2 cm / 0.4–0.8 in).
• WHITE / transparent / stringy feces = EMERGENCY.
• Cause #1 (90%): Hexamita (Spironucleus vortens).
• Other causes: Camallanus (red worms at the vent), intestinal bacterial infection, food change (temporary 1–2 days), acute stress.
• Hexamita treatment: Metronidazole 400 mg/100L, 10 days + temperature 30°C (86°F) + medicated food.
• Availability: veterinary pharmacies (approx. €6 / 10g, Romania estimate) or JBL Spirohexol Plus 250 (approx. €23, Romania estimate). Check local availability/pricing in your market.
• Important: treat the WHOLE AQUARIUM, not just the affected discus (the parasite is contagious).

What you'll learn from this guide

White feces in discus (Symphysodon) are one of the most serious and well-known clinical signals — in 90% of cases they indicate Hexamita (Spironucleus vortens), a flagellated protozoan that colonizes the digestive tract and multiplies exponentially under stress. Telling them from normal feces (brown, compact, short 1–2 cm / 0.4–0.8 in) is simple: white, transparent, stringy feces (long and thin like a thread) or with pieces of mucus = an emergency. This guide shows you 5 possible causes, differential diagnosis, the standard Metronidazole treatment and when to suspect other diseases (Camallanus, bacterial infection).

Normal vs abnormal feces — a diagnostic gallery

The 5 possible causes

1. Hexamita (Spironucleus vortens) ⭐⭐⭐⭐⭐ — 90% of cases

The most common and best-known cause.

Life cycle:

• A flagellated, microscopic protozoan
• Lives latent in the gut of healthy discus
• Activates massively under stress (temperature under 28°C / 82°F, poor parameters, a weak diet, overcrowding)
• Multiplies exponentially → destroys the intestinal lining → malabsorption → weight loss

Associated symptoms:

• ✅ White feces, long, stringy
• ✅ Food refusal or a gradual drop in appetite
• ✅ Visible weight loss (sharp back, sunken belly)
• ✅ Pale or darkened colors
• ✅ In an advanced stage: holes in the head (HITH) — Hole In The Head

Full details: Hexamita and HITH

2. Camallanus (red intestinal worms) ⭐⭐

Rarer in captive-bred discus (more common in wild fish or with contaminated live food).

Pathognomonic sign: a RED worm visible sticking out of the vent (5–15mm / 0.2–0.6 in).

Treatment: Levamisole — see internal worms

3. Intestinal bacterial infection ⭐⭐⭐

Caused by pathogenic bacteria (Aeromonas hydrophila, Pseudomonas) or an imbalance of the gut flora.

Signs:

• White-gray feces, sometimes with mucus
• A swollen belly (gas + fluid)
• Lethargy

Treatment: Metronidazole + a broad-spectrum antibiotic (eSHa 2000) combo.

4. Recent food change ⭐⭐ — temporary 1–2 days

A sudden switch from pellets to beef heart or vice versa can cause temporarily lighter feces.

Key difference: the white returns to normal within 24–48 hours + the fish is active and eating. If it persists >2–3 days → suspect Hexamita.

5. Acute stress ⭐⭐ — rarely

Strong stress (transport, a major intervention, aggressive new fish) can unbalance digestion for 1–2 days.

Difference: it resolves on its own when the stress goes, no treatment needed.

Quick diagnosis — Hexamita feces vs others

Hexamita confirmation (90% probability)

✅ Long, thin, stringy feces (>5 cm / 2 in long, 1–2 mm thick) ✅ White or transparent color ✅ Persists for days / weeks ✅ + food refusal or drop in appetite ✅ + gradual weight loss ✅ + pale/dark colors ✅ + in an advanced stage: holes in the head (HITH)

Telling it from others

• Visible red worm → Camallanus (NOT Hexamita)
• Hard swollen belly → bacterial infection (Metronidazole + eSHa 2000 combo)
• The white disappears in 1–2 days, fish active → food change (no intervention)
• Bubbles in the feces → fermentation (check the food, may be spoiled)

Hexamita treatment — full protocol

Phase 1 — Preparation (day 1)

1. Remove the activated carbon from the filter (it absorbs the Metronidazole)
2. Check the temperature — target 30°C / 86°F (NOT 32°C / 90°F, too hot)
3. Extra aeration (Metronidazole consumes O₂)
4. Reduce feeding by 50% (affected gut)

Phase 2 — Metronidazole in the water (days 1–10)

Prices are Romania estimates — check local availability and pricing in your market.

Phase 3 — Medicated food (if it's eating)

Much more effective than water dosing alone — the Metronidazole reaches the gut directly.

Recipe:

• 100g beef heart mix or soaked pellets
• 0.5g Metronidazole powder (weighed precisely)
• 2 cloves fresh crushed garlic
• 1 teaspoon of a vitamin supplement

Feeding: 2× / day, 10 days.

Phase 4 — Support treatment

• ✅ Temperature 30°C (86°F) stable
• ✅ Catappa leaves (1 / 50L) — a natural anti-protozoan
• ✅ Vitamin supplement (gut flora recovery)
• ✅ 30% changes / day (eased toxins)

Phase 5 — Post-treatment (days 10–20)

• 50% water change + NEW activated carbon (absorbs residues)
• Probiotics (Sera Bactopur Direct or continued garlic)
• Observe for 2 weeks for a relapse

Treat the WHOLE aquarium

Hexamita is contagious between discus. Even if only one has visible symptoms, the others are probably asymptomatic carriers.

❌ Don't isolate just one discus and treat it alone — the rest stay carriers ✅ Treat the whole aquarium with Metronidazole in the water + medicated food

Hexamita prevention

Common mistakes

❌ Treating only the discus with symptoms — Hexamita is contagious, treat the whole aquarium

❌ Stopping treatment after 5 days because "it seems better" — a guaranteed relapse

❌ Activated carbon in the filter during treatment — absorbs the medicine, zero efficacy

❌ Temperature 32–34°C (90–93°F) — dangerous, it doesn't speed up Hexamita treatment

❌ Using only "natural" products (catappa leaves alone) — insufficient for advanced Hexamita

❌ Waiting 2 weeks thinking it resolves on its own — the disease advances fast

❌ Not testing the water — often a triggering stress (high NO₃, low temperature)

Final checklist — white feces in discus

• ☐ Confirmed: white + stringy feces (not just slightly lighter)
• ☐ Checked for other symptoms (food refusal, weight loss, colors, HITH)
• ☐ Ruled out other causes (red worm = Camallanus, swollen belly = bacterial)
• ☐ Removed activated carbon from the filter
• ☐ Temperature set to 30°C (86°F)
• ☐ Extra aeration turned on
• ☐ Bought Metronidazole (vet pharmacy or JBL)
• ☐ Started treatment at 400mg/100L
• ☐ Prepared medicated food (if it's eating)
• ☐ Treating the WHOLE aquarium (not just the symptomatic one)
• ☐ 30% changes / day throughout
• ☐ Documented the evolution (daily photo)
• ☐ Post-treatment: new carbon + monitor for 2 weeks

What to do next

📚 Continue learning:

• Hexamita and HITH — the detailed protocol
• Internal worms — for red worms
• The aquarist's pharmacy — Metronidazole and alternatives
• Discus not eating — a correlated symptom
• Simple quarantine — prevention

🔧 Practical resources:

• Visual diagnosis
• Treatments — shop
• Premium food — shop

🐠 Final tip: White feces are one of the few situations in fishkeeping where you act fast without waiting too long — Metronidazole doesn't hurt if you got the diagnosis wrong (it's well tolerated by discus), but a delay can be fatal. Treat the whole aquarium preventively when you see symptoms in 1 fish — you save weeks of struggle and rescue more discus.