How big is your Mbu, out of curiosity? What I found was that when he was younger, ours was not as bold about what he would and would not do. There is a huge difference between what a, say, 12" Mbu will try versus what a 20"+ Mbu will try. The issue is that big Mbu want to "sample" everything in their environment and they do this, of course, by biting it. Could be an eye, could be a tail, could be anything. Mine has bitten through thermometers, air lines, and anything else that sparks his curiosity.
I would just hate to see a nice ray get it's eye eaten out by a puffer when it could have been avoided. Of course, there are no guarantees about any of this but search the forums for "Mbu and ray" and you will find some interesting stories.
