Well, in defense of this admitedly silly idea, you have to concede that even a dragon wouldn't be too keen on eating an exploding meal...
I really can't see ANY predator attacking these things when they're floating. Sure, maybe the largest dragons creatures of like size and power may be able to stomach them or deal with the explosion (though even they would be likely to search for easier prey), but anything smaller would either be killed or be taught a very painful lesson it wouldn't forget soon. Animals learn behaviors, too.