What do you use in the middle of your balls? I attempted one a while back with sphagnum moss that I had left over from some carnivorous plant stuff, it kind of worked but there was a lot of debris, maybe the moss was too cheap a quality. Those look really nice though, I have a bunch of floating stems in one of my tanks and this might be my next project.
It is sphagnum moss. It's taken much experience to get them to this point.