Something changed.
Let's start there.
Use the fish's condition to choose the next step. A symptom is a reason to investigate, not a diagnosis.
Choose the closest situation
What are you noticing?
These are routes to first checks, not diagnoses. Several problems can produce the same visible sign.
Start with the environment
Observe the fish and check the essentials.
Check working aeration, filtration and temperature; test the water and record the results. Severe or worsening distress needs prompt advice from a veterinarian who treats fish.
Follow the first checksMake the next conversation usefulBring the timeline,
Bring the timeline,
not a guess.
Keep notes on the species, when the change began, water readings with units, equipment and anything recently added or changed.
Avoid mixing treatments on the strength of an image. A clear history helps a professional assess the actual problem.
01 / The fish & the signs02 / Readings, units & test time03 / Filter, aeration & temperature04 / New animals, products or maintenancePrepare the full case history