my puffer swims over the BTA but hes never eaten it, either the clownfish defends it too well or he just isn't interested.
The hermit crab/invert issue is weird, I've heard about puffer's that are ruthless crab and snail killers and also ones that never give crabs a second look.
I think a good rule of thumb is that if your crab has a shell his chances of surviving are higher. Not guaranteed, but higher. Bigger crabs last longer also.
And shrimps are a no no, I'm pretty sure I know how my CBS died and I'm glad I wasn't there to witness it, poor shrimp
My puffer did have a thing for sucking my hawaiian zebra hermits out of their shells though, i think i have all of two left of them.
Pufferfish = lots of sacrifices (as far as what you can keep in your tank and what you cannot)