I know there are already some threads on this, but I just want to be absolutely sure that I do this right. I would hate to make a mistake and have something go wrong. I have a 20 gallon tank with a topfin 20 filter on it. Now that I'm putting more fish into the tank, I want to upgrade the filter. I am planning on getting the AquaClear 50. What is the best way to switch them out? I was thinking of either running them both at the same time for a few weeks, or just shoving the old filter media into the new AquaClear 50 (I don't plan on using the carbon, so there should be some extra room in there). Is either option better than the other? Or maybe something else I didn't think of? If the best solution is putting the old filter media into the new filter, do I do the black sponge and the white filter? Or just one of them? You can see the sponge and filter that come with the topfin here: . Another interesting thing to note is that my topfin is currently setup like picture one on that link, even though the claim is that picture 2 is correct. Not sure if I've been doing it wrong this whole time... Any help is appreciated!