Behaviour & health
Fish gasping or breathing rapidly
Treat breathing distress as urgent, particularly when more than one fish is affected.
Check the system now
Confirm circulation and aeration are actually working. Increase safe aeration where possible and get prompt expert advice. Keep yourself safe around water and electrics.
Test the water
Record ammonia, nitrite, pH and temperature. If you can measure dissolved oxygen correctly, include that result. Poor chemistry and gill problems can also cause breathing signs, so apparent aeration does not exclude illness.
Pause the shopping plan
Do not add new fish or increase feeding while investigating. Avoid adding several chemicals on the assumption that one might help.
Explain what changed
Tell the adviser when it started, which species are affected, whether it is worse at dawn, and whether a pump stopped, algae died, water was changed or a treatment was used. Urgent practical help is more valuable than a photo identification.
Describe the breathing problem clearly
Note when it began, whether all fish are affected and where they are gathering. Share your current water results and whether air and water flow are running. Do not delay urgent help while assembling a perfect record.
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.