Symptoms & urgent help
Lumps, tumours and growths
Fish can develop benign and malignant growths. A lump cannot be classified reliably from a photograph alone.
Follow the change
Record where it is, whether it grows and whether it affects swimming, breathing or eating. Take comparable photographs without repeated handling.
What a vet may offer
Examination and sometimes imaging or tissue tests can distinguish possibilities. Treatment options depend on the location and diagnosis.
Do not remove it yourself
Avoid cutting, squeezing or burning growths. A small stable lump and a rapidly ulcerating mass need different assessments.
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.