Check adult requirements
Record the baseline and check the species’ day or night rhythm. Do not infer the aquarium's condition from a single sign. Confirm scientific identity, adult size, diet, social behaviour and swimming zone.
Then compare usual posture, colour and resting location with livestock needs and recent changes. Look for genuine overlap in water, flow, territory and feeding throughout the year.
Assess compatibility and welfare
Adjust one variable and assess rest versus abnormal breathing or balance before continuing. Keep a reference so the result can be compared. Plan the complete group and monitor feeding, breathing, injury, shelter and space use.
Do not tap glass or flash bright light to check whether a resting fish is alive.