Behaviour & health
Flashing, rubbing or repeated flicking
A fish rubbing against a surface may be irritated. The behaviour alone does not identify the cause.
Record the pattern
Note whether it is one fish or several, occasional or frequent, and whether it began after a water change or new arrival. A short video can help describe the movement.
Start with water quality
Check ammonia, nitrite, pH and temperature and review recent additions to the water. Do not assume parasites before checking for a husbandry cause.
When a scrape may help
A competent fish-health professional may recommend examination and microscopy. The technique, sample handling and interpretation matter. Avoid repeatedly catching or scraping fish without suitable training.
Before treating
Confirm the diagnosis, exact pond volume and all species present. Seek advice about product compatibility. A treatment chosen from a single behaviour can delay the right help or cause additional harm.
Make the observation specific
Record which fish rub, how often it happens and whether appetite or breathing has changed. Include recent treatments and water results. A video and a timeline are more useful than selecting a parasite from a photograph online.
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.