For those of you who use your FX5 as a mechnical filter, I found this filter sponge in the clearance bin at Petsmart...was orginally $7.00 and change picked it up for a 5 spot. trimmed the outer blue ring and it's fits the FX5 basket nicely. Placed this in the top basket above the fluval ceramic and glass noodles...I'll let you know how it works...thought this was a good idea since Fluval doesn't make any pads that work for this filter currently and it augments the other sponge filter rings.