I'm hoping to build a commercial sized system that will not require too much in the way of filtration. I'm planning on stocking at low density in a rectangular tank with rounded corners. I'll pump into the tank at the sides on the long axis to induce a swirl and periodically open a bottom centre drain to get the big solids out. I'll pump from high in the water column to the raft trays and put a couple feet of some as yet undetermined filter medium at the head of each raft tray.
Just in case that doesn't work I'm going to leave room for a vortex filter.