Bottom to top : Bottom : sponge always (it will collect all dirt n particles n poop ) Mid : media (ceramic ring or bio home ).....*bio home very expensive n not easy available in India Top : activated carbon + (bio ball or ceramic ring ) Other than this I also put some ceramic rings in the base of the canister filter....so that it catches all large poops n particles even before it reaches sponge

Kindly chk my another canister filter video wher I have explained proper sequence of placing media

Thanks☺