well.. there's a bit more to the material in the biowheel, and all biological filteration medium, not only does it have to last a long time, and stay moist it has to have alot of surface area, for bacteria colonies. bio balls for example [taken from that petplace]
'One gallon of Bio-Sponge Balls has enough surface area to provide biological filtration for approximately 50 gallons of marine life. There are approximately 40 Bio-Sponge Balls per gallon and each Bio-Sponge Ball has a surface area of approximately 75 square inches.'
True you could use almost anything for this function, some people use piles of plastic drinking straws cut in half, others use straw/hay for bio-media, some other people use sponges, or live rock. there are a bunch of choices, if anything don't limit yourself right now on the biowheel materal. worse case scenario you could always throw in a few handfuls of Bio Chem Stars, [they're pretty much a sponge shaped like a star and provide more surface area than bioballs, mentioned above] to solve the problem.