Um...isn't the cotton side of the cartrige supposed to get plugged? That's you're macrofiltration, right, suppose to capture debris? Then you rinse the cartrige off when you do your water change, and bingo, good as new. I've used marineland fliters my entire career (Have the nice retail systems at my ol' shop!) and have had no problems beyond the basic ones you encounter in any filtration system. Aqua clear sponges can get just as clogged depending upon how much crap you have in your tank. *shrug*
~~Colesea