Camallanus worms are intestinal nematodes that cause red, thread-like worms to protrude from the fish's anus. Common in livebearers (guppies, mollies, platys) and African cichlids. Infected fish may appear healthy initially but slowly waste away.
Levamisole HCl is the gold-standard treatment. Dose 2 mg/L for 24 hours, then 50% water change. Repeat in 14 days to kill new worms hatching from eggs. Alternative: Fenbendazole (Panacur C) 0.1g per 10 gallons for 3 days, repeat in 14 days. Vacuum substrate aggressively after treatment - dead worms + eggs settle to bottom.
Camallanus is rare in saltwater. If present, same protocol: Levamisole or Fenbendazole. Check the tank source - usually came in on a freshwater plant introduction.
Quarantine all new livebearers + cichlids 4-6 weeks. Avoid live tubifex or blackworms from unknown sources (common vector). Treat new fish prophylactically with Levamisole during quarantine.
Estimated cost: $15-30.
Yes if untreated. The worms compete for nutrients and can cause intestinal blockage. Severe infections lead to wasting + death over months. Mild infections may not be visible externally - fish appear healthy but slowly decline.
The single most important disease-prevention step: a 4-6 week quarantine of every new fish before adding to your display. See the complete quarantine protocol.