I have the same kind of filter. I always just take off the filter lid, lift the old one out, plop in the new one and prop the old one in behind the new one about halfway down the water's surface. It doesn't look good for about 5 days, but I don't like to take chances. After 5 days I just take the old one out and replace the lid. I change it about every 3-4 months. I'm guessing I do it right, since I've never had a problem with it before (ammonia/nitrites), however I've been doing some stupid things as of late.
The Bio-Wheel is supposed to trap the bacteria guaranteed it stays in semi-constant motion (stays wet), but I don't trust it that much. If I am correct in the way I change the filter (someone chime in if you think I'm a buffoon), then you are right on!
