Here's my take on volonia.
Let's assume that a particular crab or fish could eat BA. BTW, in interests of full disclosure, IME mithrax crabs, foxfaces, or anything else do not eat valonia.
Based on my experience with dozens of mithrax from multiple sources, I am especially confident that they eat LPS polyps before they touch BA.
But if any such herbivore ate volonia, how would it do so? It sure can't swallow the stuff whole. So it would tear into the BA with its mouth, burst it, and then eat the remnants, right?
Assuming that's the case, then what is the problem with removing the BA by tearing it apart with a metal or wooden probe and siphoning out the remnants while doing water changes? Works for me.
Good luck,
Mike