************** I have a genuine fluval pre-filter sponge on my 29 gallon with Fluval C3. It is almost essential when using the fluval C series since, unlike the aquaclear, the entire polyfoam pad must be replaced and cannot be rinsed clean.
http://www.aquariumadvice.com/forums/f60/fluval-c-series-poly-foam-pad-not-reusable-sharing-my-experience-280070.html [In an aquaclear, you can of course put polishing pad or floss in the carbon chamger to get the same result.] The fluval pre-filter sponge also fits on the AquaClear series. Bottom line is the sponge pre-filter lasts forever and is great because it: 1) keeps debris out of your filter reducing replacement of media. 2) builds its own colony of beneficial bacteria ..... thus you can rinse it in clean aquarium or distilled water at times that don't coincide with cleaning of your filter or replacement of media within your filter. The pre-filter concept is great on my aqua-tech on my 38 gallon as well. I use a bio bag "casing" filled with floss so water in the "dirty water" chamber is pre-cleaned ..... which enables me to put seachem purigen and seachem matirx BEROFRE the water passes through the regular aqua-tech filter elements ... to which I also add 100 micron polishing pad. Note: I plan to replace my 330 GPH aqua-tech on my 38 gallon with a fluval c3 + aquaclear 50 within the next few months.