It depends on how you're running your QT. Are you using it to treat or just to keep things isolated before putting it into your DT. For our QT which we rest our new fish or coral pieces before going into the DT... We used block media, carbon in a media bag, sometimes swap for chemiclean depending on what's happening in the tank if we treat the tank with any type of chemical we pull everything rinse and readd it's worked out well for us thus far. We don't typically use sponges anymore due to any type of chemical treatment that might need to be done to the tank they just become throwaway in my opinion (not against them I would just like to save a sponge