Sponges that come with HOB filters (like the AquaClears) are great for this, since I don't use them in my filters, but get a nice block when I buy a new filter.
Heavy duty shears or scissors, cut into chunks/strips or whatever you need to fill a gap...I use them for this purpose in non-aquarium situations, as well.
Heavy duty shears or scissors, cut into chunks/strips or whatever you need to fill a gap...I use them for this purpose in non-aquarium situations, as well.
