Come to think of it though, I did try a couple of real small white dusters - about 1/2 inch across. They mysteriously met their fate and I couldn't tell why. The larger ones, 3-4 inches across are doing just fine. Maybe the smaller ones were too easy for hermits or fish to be attracted to. And I've got reef friendly fish.
Moral of the story might be that size does matter.
"Life may not be the party we hoped for but while we are here we might as well dance!"