I see...But when I open up my fluval the top basket has a lid which has a small raised ring protruding from the top which mates up with the return pump on the motor housing,so wouldnt this cause the flow of water to be directed through the media baskets.The motor housing will not close on to the media basket properly unless they are mated exactly and the fit seems somewhat snug.I have never had the chance to use an ehiem so I am not quit sure how they ensure the flow through the media.