If it is an insulated trigger you can forget about keeping anything with him unless you have a massive tank. He WILL eventually go crazy and kill ALL his tankmates. I would definitely return him.
Yeah everything is going to the new tank. Really? It's that simple I mean I figured it was but I've heard of people's tanks crashing from doing an upgrade
I'm not sure on puffers realising toxins I know box fish do. But from what I've read and been told puffers and triggers are not good tank mates for cat sharks or rays since they peek at their eyes and fins.