You don't even need to save the frame, necessarily. You can save money by buying some filter sponge, maybe one for an Aquaclear, and cut it to fit the Aqueon, leaving some room at the top for some filter wool or filter floss, same thing, different ways to describe it.
If there is room you can also add a mesh bag of ceramic media as well. All three of these media grow BB well, can be cleaned and reused over and over again. Just squeeze out, swish and rinse in tank water, not tap water.
Floss will eventually get pretty raggedy, and if so, you can replace it at that time. It will turn grey, that's normal, but it works quite well to polish the water, as it catches even tiny particles that may make water look less clear.
The cartridges that are sold as refills for filters are mainly making money for the makers of the filters. And most contain carbon which you do not need. Unless you are trying to remove medication, discolouration or nasty odours from the water, carbon is simply not needed.
