If you keep tilapia intensively, you need a way to remove the particulate matter. Grow beds are the best, but if you want to use a floating raft system, you need filtered water anyway.
I start with Sterilite stacking containers from Walmart:
I drill out large holes in the bottom of two of them, and in the sides of a 3rd one.
I cut and glue plastic screen cloth to the bottom using hotglue.
You'll find this in craft stores and it is used to make hand hooked rugs.
My containers stack leaving about 4" space. If yours don't cut 4" section of PVC pipe to use as standoffs. The bottom container keeps the 2nd level out of the water, or just partially submerged. The 2nd container is filled with plastic scrubby pads for the dollar store. Pack them tightly, but don't let them crush. These will be the primary bio-filter, just like bios balls but a lot cheaper.
The top container is filled with plastic filter beads, ones that sink.
I put another layer of the plastic screening on top to keep the beads in place. This whole contraption goes in my sump:
I drill a hole near the top and put in an overflow pipe for when the filter clogs up. This keeps down the splashing. When this happens you can still the top layer of beads to break up the particles to buy you another day between cleaning.
Cleaning is simple. Remove the bead container. Run water through while stirring the beads. The dirty water can be dumped into your grow beds.
The filtration is fantastic.