I have a Hagen Aquaclear. I am a little confused by 'using something in it's place'. Like something that does something similar like the Ammo chips? Or something that takes up the space that the carbon would have went?
Since my filter is set up differently than the typical 'slot' type with the replaceable carbon inserts, the absence of carbon just means I have more room for sponges and ceramics to stack.
And as an fyi, if you choose to go with carbon, if you don't change it out once a month you might as well put ceramics in instead. After it is not 'actively working' it just becomes a place for the good bacteria to grow, and good bacteria can grow better on ceramics.