You can use filter pads to help clear out the smaller debris that would otherwise bypass a regular filter sponge. Filter floss does a good job as well, Both are much cheaper in places like a craft store instead of buying them in a pet store.
I use pads that I cut to size and Purigen. I like my fish to look as though they are suspended in air, so I get the whole water clarity thing.
I think this floating things in a tank to clarify water is new trend in pet stores. I read somewhere somebody tried to float a bag of Purigen in their tank, then complained that it didn't work. Of course it didn't work, it needs to go in the filter.