I had some pipe insulation foam left over from a surfboard rack I made. I cut about a 1-inch by 1/2-inch section, rolled it like a foam ear plug and shoved it into the hose. Worked like a charm. The foam is very dense, so I have no fear of it breaking down and crumbling inside the hose. As others have said here, almost anything that will fit will work, but I liked the idea of using something that I could compact and then would expand to fill the space.