When the sphagnum moss grows its more compacted, so it tends to be better. When I first replace it I try to press it down so its not so light. I think that helps. Also i have bits and pieces sitting on it. Moss Mounds are great for coverage to. In their natural environment I would imagine they swallow all sorts. All I know is that Ive used it for 5 years and had no problems so far.(touch wood)