fish

Anchor Worm (Lernaea)

A parasitic copepod (not a true worm) that embeds in fish skin, causing visible red lesions and secondary infections. Common in ponds. Treatment: manual removal + dimilin.

Symptoms

Thread-like parasite with a forked anchor end protruding from the skin.
Red, swollen lesions at attachment points; visible blood spots (E1).
Secondary infections at wounds in heavier infestations.

Common Causes

A parasitic copepod — not a true worm (E1) — that embeds in fish skin.
Common in pond fish and introduced with new stock (E1).
Skin embedding causes lesion damage that invites secondary infection.

What to Check

Look for the trailing thread on the body — it is the diagnostic sign.
Check recent additions, especially pond-raised fish.
Plan both physical removal of adults and a treatment for free-swimming stages (E1: manual removal + dimilin).

What Not to Do

Do not pull adults out and stop there — larvae remain in the water column.
Do not treat the water without removing the embedded females — they release more larvae.

This guide is informational and does not replace professional veterinary advice. If fish are severely ill, consult a veterinarian.

Anchor Worm (Lernaea)

Symptoms

Common Causes

What to Check

What Not to Do

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Anchor Worm (Lernaea)

Symptoms

Common Causes

What to Check

What Not to Do