parasite · pond-mostly

Anchor Worm (Lernaea)

Anchor worms (Lernaea) are visible white-green parasites (0.5-1 inch) protruding from fish skin like tiny spaghetti. Common in koi + goldfish. Treatment: Dimilin + manual removal.

Severity: Moderate - visible + uncomfortable but treatable

Symptoms

Visible white/green worm-like protrusions on fish
Inflammation at attachment site
Fish scratching against objects
Secondary bacterial infection at bite sites

Cause

Lernaea parasites attach to skin + burrow embedded "anchor". Common in pond fish.

Treatment

Always treat in a separate quarantine tank. Most medications are toxic to coral, invertebrates, and live rock biology.

Diflubenzuron (Dimilin). Single pond-wide treatment kills all life stages. Most effective for outbreaks.

Manual removal. Net fish, grasp anchor worm with tweezers, pull straight out + dab iodine on wound. For small infestations.

Potassium permanganate. Bath treatment kills external parasites. Repeat 7 days later for hatching cycle.

Prevention

Quarantine new pond fish 21-30 days. Treat prophylactically with Dimilin in spring.

Browse the full disease database for 45 aquarium conditions with treatment protocols, or check the care library for prevention-focused husbandry guides. Use our symptom matcher to rank likely diseases from observed signs, the water parameter checker to diagnose related water-quality issues, or the QT timeline calculator to plan a treatment schedule.

Anchor Worm (Lernaea)

Symptoms

Cause

Treatment

Prevention

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