A Repeatable Check
The useful question is what changed in your particular aquarium. Check the relevant label or manual, note the current condition, and compare with an earlier observation made using the same method.
For equipment, use the exact model manual, check the path from power or intake through to output, and confirm normal flow after service. Keep electrical parts dry and preserve established media when appropriate.
A Practical Routine
Finding the Correct Media Order for a Filter is easiest to evaluate when the setup is stable. Use the same sample source or equipment position for comparison. Note the date, what was changed, and any recent maintenance; this keeps a personal observation useful without turning it into advice for every tank.
Avoid adding chemicals or replacing several established parts based on an uncertain observation. If the issue continues, consult the manufacturer or a qualified aquarium professional with your notes. For equipment, use the exact model manual, check the path from power or intake through to output, and confirm normal flow after service. Keep electrical parts dry and preserve established media when appropriate.
Use these as general hobby references. Test your aquarium and confirm product guidance before making changes.