Internal worms in discus: Camallanus, Capillaria — treatment

In short

• Main types: Camallanus (red worms visible at the anus), Capillaria (fine white, microscopic threads), tapeworms (rare).
• Source #1: contaminated live food (live tubifex, live bloodworms) or new fish without a quarantine.
• 100% diagnosis: red threads protruding from the anus = Camallanus. Chronic weight loss + white feces = Capillaria or Hexamita.
• Nematode treatment (Camallanus, Capillaria): Levamisole 1–2 mg/L of water × 24h, repeat at 14 days.
• Tapeworm/fluke treatment: Praziquantel 2–5 mg/L, 7 days.
• Most effective: medicated food (the medication goes straight to the gut).
• Repeat the treatment after 14 days — the eggs survive the first cycle.

What you'll learn from this guide

Internal worms in discus are one of the main causes of chronic weight loss and gradual food refusal. Unlike Hexamita (a protozoan), here we're talking about multicellular parasites — nematodes (Camallanus, Capillaria), cestodes (tapeworms) and, more rarely, trematodes (flukes). They almost always come from contaminated live food or new fish introduced without a quarantine. This guide shows you how to recognize each type, which medication to choose (Levamisole for nematodes, Praziquantel for tapeworms and flukes), how to prepare medicated food (more effective than a bath) and how to prevent reinfestation.

Types of internal worms in discus

⚠️ Important: Hexamita is NOT a worm, it's a protozoan. Many losses come from a wrong diagnosis — treating white feces with Levamisole when it's actually Hexamita = a loss of critical time.

Where internal worms come from

Symptoms — how to recognize internal worms

Camallanus (red worms) — 100% visual diagnosis

• ✅ Red-brown threads protruding from the anus (length 0.5–2 cm / 0.2–0.8 in)
• ✅ A slightly inflamed, red anus
• ✅ Gradual weight loss
• ✅ A fickle appetite — sometimes eating, sometimes refusing
• ✅ Feces sometimes with blood or red segments

Parasite traits:

• Feeds on the fish's blood
• Very contagious through feces
• Visible to the naked eye

Capillaria — a difficult diagnosis

• ❌ Very slow weight loss (weeks–months)
• ❌ White or stringy feces
• ❌ A gradually dropping appetite
• ❌ Fry with stalled growth
• ❌ Pale colors

Confirmed diagnosis: microscopic only (eggs in the feces).

Tapeworms (rare in discus)

• ❌ Flat white segments visible in the feces
• ❌ A slightly swollen belly
• ❌ Weight loss with appetite intact (the fish eats but doesn't gain weight)

Flukes (microscopic)

• ❌ Excess mucus on the gills
• ❌ Fast breathing
• ❌ Rubbing on decor ("flashing")
• ❌ Clamped fins

Differentiation — worms vs other causes

Treatment — step by step

Step 1 — Diagnose correctly

• You see red worms at the anus → Camallanus (Levamisole)
• White feces + fast weight loss → suspect Hexamita (Metronidazole)
• Chronic weight loss, no longer sure → a combined treatment (see below)
• Fry with stalled growth → suspect Capillaria + Hexamita

Step 2 — Levamisole (Camallanus, Capillaria) ⭐ RECOMMENDED

Available products

(Romania estimate: eSHa NDX approx. €13–19, Tropical Antibac Pro approx. €9, Levamisole powder approx. €9–15 / 10g.)

Medicated-bath protocol

Full schedule (28 days):

1. Day 1: add Levamisole 1–2 mg/L
2. Day 2: 50% water change + INTENSE floor vacuuming (the dead worms)
3. Days 3–13: observe, 30% changes / week
4. Day 14: identical re-dose (the second generation of worms)
5. Day 15: 50% change + vacuuming
6. Days 16–28: monitoring, a varied diet with a multivitamin

🧮 For the exact dose on your aquarium's real volume (minus substrate and decor), use the treatment calculator.

Step 3 — Praziquantel (tapeworms, flukes)

Available products

(Romania estimate: JBL Spirohexol approx. €23, API General Cure approx. €15, eSHa 2000 approx. €9–15, Praziquantel powder approx. €17.)

Protocol

Step 4 — Medicated food (MORE EFFECTIVE than a bath)

For internal worms, medication in the food goes straight to the gut — effectiveness rises 3–5×.

Requirement: the fish must still be eating. If it has completely refused food → a bath is mandatory.

Levamisole recipe (Camallanus, Capillaria)

Preparation:

1. Soak the pellets in 10 ml of water (5 min)
2. Mix well with Levamisole + garlic + multivitamin
3. Form small pieces (0.3–0.5 cm)
4. Freeze in a thin bag
5. Feed 2× / day, 3 consecutive days
6. Repeat the cycle after 14 days

Praziquantel recipe (tapeworms, flukes)

Feed 2× / day, 7 consecutive days. Repeat after 14 days.

Step 5 — Combined treatment (when you're not sure)

For ambiguous cases (chronic weight loss, no visible worms, variable feces):

Common mistakes

❌ A single treatment cycle → the eggs survive, the worms come back in 2–3 weeks. Always 2 cycles 14 days apart.

❌ Carrying on with live tubifex / live bloodworms → immediate reinfestation. Switch fully to frozen.

❌ Not isolating the affected fish → the whole group exposed. With Camallanus, contagiousness through feces is at its maximum.

❌ Stopping feeding "so I don't feed the parasites" → weakened fish die of starvation faster than from parasites. Feed a varied diet.

❌ Self-diagnosing white feces = worms → in 70% of cases it's Hexamita. Levamisole does NOT work on Hexamita.

❌ Leaving activated carbon in the filter → it absorbs the Levamisole/Praziquantel, zero treatment.

❌ Not vacuuming the floor after the bath → the dead worms release eggs into the substrate → reinfestation.

❌ Mixing Levamisole + Praziquantel at the same time → cumulative toxicity. Use the ready-made combos (eSHa NDX) or separately, 14 days apart.

Prevention — how to avoid internal worms

See also simple quarantine for beginners and common beginner mistakes.

When to consult a specialist

• Unknown visible worms (a different look than Camallanus)
• Symptoms persisting after 2 complete cycles
• Mortality starts to appear
• Affected fry (difficult treatment, sensitive doses)
• Other symptoms appear at the same time (Ich, Columnaris, Dropsy)

Post on dedicated forums with photos (anus + feces + water parameters) or contact breeders from the discus.ro directory.

Final checklist — managing internal worms

• ☐ Identified the type (Camallanus / Capillaria / tapeworms)
• ☐ Checked the source (live food? new fish?)
• ☐ Eliminated the source (switched to frozen food)
• ☐ Removed the activated carbon from the filter
• ☐ Started Levamisole (1–2 mg/L) OR Praziquantel (2–5 mg/L)
• ☐ Max aeration
• ☐ 50% change + INTENSE vacuuming after the bath
• ☐ Scheduled a re-dose on day 14
• ☐ Post-treatment: multivitamin for 2 weeks + garlic 2× / week
• ☐ Monitored the feces for 4 weeks
• ☐ Fresh activated carbon after finishing
• ☐ Checked whether other fish are affected

What to do next

📚 Continue learning:

• Hexamita and HITH in discus — white feces = often Hexamita, not worms
• Ich (white spot) — another common parasite
• Bacterial gill infections — other causes of weight loss
• The essential aquarist's pharmacy — a complete kit
• Simple quarantine — prevention #1

🔧 Practical resources:

• Treatment dose calculator — exact Levamisole, Praziquantel
• Visual diagnosis — at the first signs
• Aquarium treatments — shop — eSHa NDX, JBL Spirohexol

🐠 Final tip: Internal worms are 95% preventable with a quarantine + frozen food. The cost of a 4-week quarantine is laughable compared to the cost of treatment + the mortality risk. Discipline on the inputs (fish + food) matters more than any medication.