External parasites
Epistylis, Apiosoma and attached ciliates
Attached ciliates can resemble small colonies on fish tissue. Appearance can overlap with other surface problems.
What microscopy adds
Epistylis forms stalked colonies; other sessile ciliates have different shapes. The linked UF/IFAS guide helps an examiner compare them.
Check the surroundings
Heavy organic loading can be relevant. Record the sample location and review waste removal as part of the investigation.
Avoid white-spot shortcuts
Do not choose medication from a white-dot photograph alone. Ask whether there is damaged tissue, a bacterial component or a separate parasite requiring attention.
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.