External parasites
Skin flukes: Gyrodactylus
Skin flukes are monogenean flatworms. Gyrodactylus commonly gives birth to live young, so population growth can be rapid.
Confirm which fluke
A wet mount can show the attachment hooks and developing young. The keeper names “skin” and “gill” fluke are useful shorthand, but location alone is not definitive identification.
Plan the whole course
Ask the examiner to identify the organism and set a product-specific plan for the fish present. Species, temperature and previous treatments affect the decision.
Check the result
Record dates and arrange microscopy follow-up. Repeatedly dosing without checking can miss another cause of continued irritation.
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.