Not too sure what the "+" media is like... I have an old Fluval 3, and it uses a foam cylinder... which lasts YEARS ! and is only £4 for 2, so I doubt you would want to cut any corners if its the same in the +.
My Eheim canister uses a coarse foam disc (similar to the fluval in density) which is resuable, then ceramic media - topped of with a fine white disc to capture smaller particles.... its this one that I use the wadding for, as because of its fine mesh, tends to get very clogged.
I suppose in theory you could use the wadding in a fluval the same as mine, because its ALL down to surface area... but as mentioned above, the real sponge is so cheap !