internal parasite
Internal parasites / wasting disease
Progressive weight loss and sunken belly despite normal or increased appetite, often with abnormal feces (stringy, white, or mucus-laden). Caused by various internal parasites including Hexamita, Spironucleus, Capillaria, or other nematodes. Common in wild-caught fish and recently imported specimens.
Do first
- Observe feces closely white, stringy, or mucus-laden feces are a key indicator.
- Move the fish to a hospital tank for treatment if possible.
- Do not attempt to feed heavily compromised fish with internal parasites often cannot absorb food efficiently.
- Do not share equipment between hospital and display tank without sterilization.
Escalate if
- Fish declining rapidly despite treatment consider whether humane euthanasia is appropriate.
- Weight loss so severe the fish cannot swim or feed effectively.
- Visible worms at the vent see camallanus-worms entry for specific protocol.
Water clues
These readings can push this pattern higher or lower in the triage result.
ammonia above zero+1
Poor water quality can worsen condition but is not the primary cause check water anyway.
nitrate above 80+2
Very high nitrate combined with internal parasites accelerates decline.
Care protocol
Follow only the steps that fit your species, tank inhabitants, and medication label.
Differentiating internal parasite types
- Hexamita/Spironucleus (protozoan): white stringy feces, wasting, sometimes hole-in-the-head; very common in cichlids and discus.
- Capillaria (nematode): white thread-like feces; can cause dramatic wasting; common in discus and wild-caught cichlids.
- Camallanus (nematode): red or pink worms visibly protruding from the vent see the camallanus-specific entry.
- Cestodes (tapeworms): extreme wasting despite good appetite; white segment-like material occasionally visible in feces.
- Definitive diagnosis requires microscopic fecal examination or necropsy.
Cautions
- Do not treat blindly with multiple antiparasitics at once.
- Some parasites require different medications incorrect treatment wastes time and stresses the fish.
Treatment protocol
- For protozoan parasites (Hexamita, Spironucleus): treat with metronidazole in food if eating, in water if not.
- For nematodes (Capillaria, etc.): treat with fenbendazole (Panacur) available in food or water formats.
- Treat for the full course protozoan treatment typically 5–10 days; nematode treatment may need 2–3 rounds.
- Maintain excellent water quality in the hospital tank throughout treatment.
- After treatment, offer highly nutritious food to help the fish regain weight.
Cautions
- Metronidazole is hard on the liver avoid repeated courses without confirmed need.
- Fenbendazole kills helminths slowly do not expect immediate improvement.
- Do not treat with both simultaneously unless advised.
Source notes
References and context notes used for this triage entry.