Yeah poly filter pads.....they are good if something goes wrong cause they change different colors depending on what it is pulling out....helps to find out whats wrong:
http://www.marinedepot.com/Poly_Fil...Media-Poly_Bio_Marine-PB1111-FIFMMEPM-vi.html
And if nothing is going wrong they are a very expensive alternative. Good to have on hand just in case, but probably not practical as an ongoing filtration option.