Best way to stack media in a can

Mechanical, biological, chemical in order of water flow...that is, the water reaches Mech. first, then biological, etc...

Basically get the big stuff out of the way first - things like plant particles and other things that may interfere with the equipment down the line. In one setup I have foam, ceramic then bioballs. Another extrnal is foam, ceramic then carbon. Think of it like a coin sorting operation - weed out the big ones first and then right down to the smallest last.