Sea Apples rock! This was actually my second one in five years... both passed peacefully without incident.
From what I've learned about the Sea Apples, it's not about when they die as much as it is *how* they die...
If they purge themselves to fend off an attacker, then it nukes the tank... but if it just dies on its own, then it doesn't seem to go into defense mode, and everything stays inside.
I have a theory that it also depends on the environment where it's living... my hallucination is that it has to get its poisonous stuff from somewhere, kinda like a clownfish taking sting cells from an anemone, perhaps?
I'm thinking that there's a lot of stuff in the real world that they ingest that they don't inside our tanks... I could be wrong, though.
Everything else in the tank is jamming right along, though!