i have heard pot scrubbers are the best for biological surface area. I was impressed so much with the statistics that i went out and bought some today for my filters. We'll see how good they work. They supposedly have like 3 or 4 times the surface area per gallon than the bioballs do. i paid $2 for 3, and bout 3 packs. I went back later and bought another pack and put 4 of these in each of my filters. i am not sure who posted the thread on them or where, maybe in the diy section, or filter section.