Internal parasites
Tapeworms and cestodes
Cestodes are tapeworms. Some freshwater-fish parasites have life cycles involving other animals in the environment.
A specialist diagnosis
Poor growth or weight loss needs a broader assessment. Faecal or laboratory examination may be more useful than a routine mucus scrape.
What to bring
Provide the food history, new-fish history and any visible material you can photograph without disturbing the fish.
Prevent recurrence
Follow the professional’s advice about feeding sources, hygiene and follow-up, as well as any prescribed treatment.
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.