You can buy the filter pads, but the cheaper way to do this is to buy a big plastic container filled with charcoal & make your own charcoal filters with a little nylon bag that you can buy. The nylon bag is only $1.19 and I picked mine up at the local petco or petsmart store. Charcoal pads are fine & are less messy than making your own charcoal bags, they are just a little more expensive (over $2 each).
I reuse the white sponges that come with the filter, just replace the charcoal every 10 days (whenever you rinse out the white sponges). The sponges pick up large pieces of stuff floating in the tank (shedded skin, minced lettuce, etc.) but the charcoal helps filter out the chemical wastes like chlorine. I like to get the big plastic box of black charcoal that is mixed with white ammonia eater pellets since that will absorb turtle-pee and help keep your tank smelling clean.
I don't buy the charcoal pads because I have 2 turtle tanks: one has a fluval 2 the other has a fluval 4 so I am constantly changing out the charcoal, especially in the adult turtle's tank since she is very messy. So I figured it was just easier to just buy charcoal for both rather than buy different things for different tanks.
