Emerald crabs will eat the bubbles, just not the large hard ones. They get em before the get big or after they break down a little. Purple Tangs eat it, but sometimes also can't break the bubbles when they get big. And, the previous 2 posts give you another solution that can work.
I have a rogue alpha wierd bicolored blenny that is eating it. Want him? No really, I wouldn't do that to you. He eats anything he can stick his mouth on. But since I have been talking bad about him on here he is starting to behave. I'm just going to keep talking bad about him just in case that has anything to do with it.