My 45 gallon tank is currently filtered by 2 old box filters one rated for 45 gallons and the other rated for 20 gallons, and while these are working okay now i only have a couple media changes left and im not sure if i'll be able to find new filter pads for them (we've had these filters since i was maybe 7-8 years old, they weren't new then, and i turn 20 in january). I'm considering buying either an emperor 280 or 400 biowheel near christmas to replace these old filters, but I was wondering if anybody can tell me what the best way to change the filters out would be because of the beneficial bacteria built up in the other filters? I know there would still be a lot of bacteria built up on the plants/gravel/decor etc but what would be the best way to change them out without having to entirely cycle the new filter to get a build up of beneficial bacteria? I'm not sure if i'm wording this correctly but if anybody knows what I'm asking I would appreciate your knowledge of the subject.