If you are using a grow bed, it serves as the bio filter. You want twice as much grow bed as fish tank. Far less will do biofiltration, but it won't remove the nitrates and phosphates. The plants do that and you need that much space to have enough plants to do the job.

Stuctured packaging is what my Aquacube is made from. It works well. Be sure you pick a mesh size of at least 1/2" so it can't clog. The down side to that is it reduces the surface area. That is why I use the bead filter over the scrubbies. You can use a fine mesh bio filter like the scrubbies if you filter out the solids first.