Are you thinking bacteria-caused rot? I'd think this would be true for cotton, silk, their blends, etc., that is, natural fabric. These balls are made of, according to the ad: "Spherical fiber filter is made of polyester, polypropylene spherical filter and acrylic fiber. " These should on paper last very long in any body of water and are usually destroyed only by UV. How do they scare us about the PE bags in the landfills - 100-250 years to decompose by microorganisms?
Anyhow, this post and link drew my attention too when it was posted because it was a first, so I read it. Sounds like the media would be worth the try. May be much easier maintenance, regenerate, vs a large piece of unyielding matt for instance.