Adding new fish to tank with puffer?

[sappho]

I have a sweet little dog-face puffer that I recently moved into my main tank. She was in quarantine with another fish and never bothered him one bit but now I try to add another fish to the main tank and suddenly my shy little baby puffer becomes were-fish and bites at him. It's not as if she's hungry, she's well fed.
I put the new fish in an acclimation box and (gently) shoved the puffer away for a couple minutes and shifted the LR around. Occasionally, my puffer swims by the box and looks longingly at the new fish but no biting.
Can I leave the fish in the box overnight or will the puffer bug him all night and stress him out? How long should I leave him in the box before I can safely add him to the tank?

 

[SnoopyDaPimp]

The fish will be fine in the box overnight. Fish are shipped in little bags across the country for days at a time. If you have a sump and the puffer is still being mean you could move one of the fish into the sump for a while.