Quick referenceCamallanus cotti is a freshwater nematode parasite that protrudes from the fish anus as small red worms. Highly contagious between fish; treat the entire tank with Levamisole.
Symptoms
Red worms protruding from fish anus
Weight loss / sunken belly
Color fade
Lethargy
Refusing food
White stringy poop
Cause
Internal nematode parasite spread through infected fish, contaminated live food, or shared equipment. Common entry point: pet-store livebearers (especially mollies, guppies, platies).
Treatment options
Levamisole HCl. Gold-standard treatment. Dose 2 mg/L (0.5 tsp per 10 gal of 10% solution). 3 doses 7 days apart. Treat the whole tank, not just visible-symptom fish.
Fenbendazole (Panacur). Alternative or backup. Can damage shrimp + sensitive snails. 0.1g per 10 gallons, 3 doses weekly.
Manual removal. For visible worms - tweezers + isopropyl swab. Only catches what you can see. Always combine with chemical treatment.
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 ALL new fish 30 days. Buy from breeder direct (avoid pet-store livebearers). Cull infected fish if treatment fails 2x.
Fatality + outcome
Moderate without treatment. Wasting + secondary infections kill the fish in 6-12 weeks. Treatment success rate: 90%+.