External parasites
Lernaea: anchorworm
Despite its name, anchorworm is a copepod crustacean. Adult females embed in the fish and may leave a visible trailing body.
What may be seen
A thread-like projection with attachment damage can be a clue. Do not confuse plant fibres or trailing material with a confirmed parasite.
Why simply pulling is not a plan
Attachment wounds can develop secondary infection, and other stages may remain in the system. Have the parasite identified and removal or treatment directed by a professional.
Follow the whole problem
Check the affected fish’s wounds and the rest of the stock. Record new arrivals and whether lice or other visible parasites are also present.
Sources & further reading
Original WakeyKoi wording, informed by the references below. Linked clinical resources explain the evidence and their scope; they have not reviewed or endorsed this website.
Related guides
Educational guidance cannot diagnose an individual fish. Breathing distress, severe injury or unexplained losses need prompt professional assessment.