My canisters contain the foam pads made for them that I use over and over for years. The water then passes through a fine mechanical/polishing media. For this I use filter floss crammed in to one tray as tight as I can get it (I use polyester pillow stuffing from the craft section in W**-Mart. This is cheap and I replace it every time I clean the filter. After that I fill the rest with biomedia. I prefer Seachem Matrix because it has more bioavailable surface area than Fluval or Eheim's biomedias. This also never needs to be replaced.
And a regular cleaning schedule!!! Too many buy into the hype that this, that, or the other media will do some kind of magic. I use matrix in my canisters and it works extremely well, however, I clean my canisters every four months. Anything longer than this schedule and my nitrates shoot up to over 20ppm. It took me a few years and mucho mucho $$$ before I figured this out (I am hard-headed). No media, however good it might be, will overcome a lack of "regular" filter maintenance!!! Filters (at least the cannister type) don't "eliminate" the "gunk" in your tank. They just concentrate the gunk inside of them. Failure to remove this gunk (by regularly "CLEANING" your filter) is hardly any better than just leaving it inside the tank in the first place.