The aqueon replacement filter cartridges are close to $4 a piece and dont last long. Its just the filter that came with the aquarim.
http://www.petsmart....NotAvailInUS/No
Hmm, yeah, I don't use those. Like I said, I use paradiso synthetic sea sponges and once every few weeks I wring half of them out in the sink, leaving one in the filter box so I don't uncycle the tank. They don't degrade or run out over time. If I need activated carbon, I bought a lot of it in bulk for like $12 and put some in an old garlic mesh sock in the filter. But I don't use activated carbon unless I'm removing a medication from the water after dosing with something, which happens like once a year. If you've got driftwood, it is useful for removing tannins to make the water clear for aesthetic reasons. I think Seachem has a product called purigen that is like a renewable activated carbon, but I've never bought it myself. I would look into it if I was using activated carbon every few weeks.
There are three purposes to having a filter:
1) Water flow
2) To provide a home (a high surface area place) for beneficial bacteria to colonize.
3) Mechanical filtration, to remove tiny debris from the water.
My filter uses the sponges as the high surface area place that houses the beneficial bacteria. The sponges also are a good grit and dust trap. When I wring two of them out and leave the third one alone (rotating which one gets left alone each time), I'm removing grit and dust without destroying my population of bacteria. The sponges were $2 and don't degrade over time, so it's a one time purchase that doesn't have a maintenance upkeep cost. I've been using the same sponges for years. By the way, my two filter brands are aqueon and aquaclear at the moment. The aqueon did come with those things you linked to, but I just threw them out and used my sponges. I callously ignored their instructions to continue to pay them $4 a month for the rest of my life.