well...my filter is a corner filter i think...and it has a rectangular 1 piece unit that acording to the manufacture's instructions should be changed every 2-4 weeks...the thing is i am on week one of cycling my tank...and when the time to replace it comes...i have to discard the whole thing and put a new one...it has a polyfiber pad (blue) on top and activated charcoal at the bottom...wouldnt i be throwing away A WHOLE LOT of beneficial bacteria along with it??? i would have to start the whole cycling process all over again everytime wouldnt i??? i wanna keep the polyfiber pad but i need to replace the activated charcoal...any suggestions??? thaaanks!!!