none
live rock and deep sand bed is the way to go
on the cannister, only thing i could find or read about for use is for activated carbon to polish the water and filter stuff out, not biological
wet/dry is different filtration. its more bilogical becuase of the bio balls will remove some bad stuff out. but removing the bad stuff out job is best done naturally with live rock and live sand. the wet/dry will need maintance plus water changes whereas the live rock and sand is mainly water changes.