Purigen & Matrix(how do you stack yours?)

Hey guys...I just want to get the genaral rule as to where & how do you guys stack your seachem In your canisters that flows from bottom-top... ? I changef mine today as follows...1st tray = black sponge with floss on top of that...(does it really matter?) 2nd tray I put the purigen & last tray I put the Matrix...I read somewhere most put their purigen on top-last just before the water goes back into the tank for better clarrity?

 

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