Diagnose the operating state
Record the baseline and check the outage duration. Do not infer the aquarium's condition from a single sign. Record timing, flow, noise and recent changes before dismantling equipment.
Then compare odour, temperature and condition of trapped water with livestock needs and recent changes. Compare the finding with normal operation and the manufacturer’s limits.
Intervene and verify recovery
Adjust one variable and assess aeration and a restart that excludes suspect water before continuing. Keep a reference so the result can be compared. Restore the system in stages and confirm stable flow, oxygenation and seals.
Discard stale canister water before restart if it smells abnormal after a long oxygen-free stop.