I wouldn't use kitchen sponges, not even the ones with the scrubber backs, since they may contain antibacterial/antifungal chemicals.
The pot scrubbers are fine http://www.aquariumlife.net/projects/diy-filter/111.asp
http://images.google.ca/imgres?imgu...using+pot+scrubbers&gbv=2&svnum=10&hl=en&sa=X