Capillaria (Stomach Worms): causes, symptoms and treatment
Capillaria (Stomach Worms) (Capillaria spp. (Pterothominx)) — etiology, symptoms, diagnosis, active-substance medication, recovery and prevention; mortality without treatment: moderate.
Overview
Hair-thin nematodes inhabiting the stomach and intestine. Common in discus, angels, and other cichlids; produce eggs visible only by microscopic faecal examination. Causative agent: Capillaria spp. (Pterothominx). Transmission: nutritional. Incubation: 21-60 days. Reported mortality without treatment: moderate.
Symptoms
- white stringy feces
- weight loss despite eating
- darkening of color
- loss of appetite eventually
- wasting
- general weakness
Causes
Outbreaks are typically triggered by chronic stress, poor water quality, temperature swings, overcrowding, or the introduction of unquarantined fish. The pathogen spreads via ingestion of infected intermediate hosts (copepods, tubifex, snails) or contaminated feed.
Diagnosis
Diagnosis is based on clinical signs (visible worms, white stringy feces, weight loss despite eating) and microscopic examination of fresh faeces for eggs or fragments of Capillaria spp. (Pterothominx).
Treatment
Effective treatment requires isolating affected fish in a quarantine tank, identifying the pathogen, administering the appropriate active substance at the correct dose and duration, and supporting recovery with stable water parameters and nutrition.
Step 1: Quarantine
Set up a bare-bottom quarantine tank with a mature sponge filter, heater, and aeration. Match temperature and pH to the display tank, and acclimate fish slowly. A bare bottom simplifies daily siphoning and prevents medication from being absorbed by substrate.
Step 2: Medication
- Levamisole or fenbendazole. Levamisole 2 ppm in water or fenbendazole 0.25% in food x 3 days, repeat after 14 days to catch larval cycles. (duration: 21 days total)
- Praziquantel. Praziquantel 2 mg/L for 7 days as alternative; less effective on capillaria than levamisole. (duration: 7 days)
Step 3: Recovery
After medication, perform a 30-50% water change and run fresh activated carbon for 24-48 hours to remove residues. Continue feeding a high-quality, varied diet with vitamins and immunostimulants. Reintroduce fish to the display tank only after at least one week without recurrence of symptoms.
Prevention
- quarantine cichlids/discus 4 weeks with deworming
- high-quality varied diet
- regular faecal examination of breeding stock
- avoid feeding wild tubifex