What's wrong with my fish?
Something looks off in the tank. Pick the symptom you're seeing and we'll show the most likely causes and the first fixes to try. Almost every fish problem starts with water quality, so if you own a test kit, reach for it before anything else.
Test first, medicate last. About 90% of fish problems are water quality, not disease. Check ammonia, nitrite and temperature before you reach for any treatment - most fixes are free.
⚠️ A starting guide, not a diagnosis. Fish can go downhill fast, so act on the water first - a partial water change rarely hurts and often helps. If problems continue after the water tests clean, look into species-specific disease guides or ask an experienced keeper. This is not veterinary advice.