I've read that it's good to rinse your filter in used tank water...but what if your filter is slimy and filthy? Is it time to change then? I have a Whisper power filter, with the white, pillowy cartridge inserts. It's only been in for about two weeks, but that thing is slimy. I tried rinsing in old tank water, but really it did no good; the stuff is really IN there. Or was I supposed to rinse the black bio-filter instead? I rinsed both because I wasn't sure. lol I wish I could get this stuff down!