Im on a roll again with my questions

I am running my Superfish Aqua Flow 50 filter in my tank (along with my Juwel filter) To change the filters on my Aqua Flow i have to buy new cartridges that click on to it. The cartridges contain a green sponge with some stones inside (carbon) I can remove the sponge from the cartridge easily.

I was wondering if it would be a good idea that when i need to change the cartridge, instead of buying new ones i could cut up a white mechanical and a blue bilogical sponge and put those inside the cartridge and change when needed.

Thank you for your reply I saw the cost for 3 replacement cartridges (which have to be changed once a month) and thought it would be cheaper just to cut up sponges.