Good chance that the clown and the harlequin bass would one day be a meal for it.
Is it possible to put two puffers in the same tank?
In a large enough tank. I wouldn't put two in a 40, especially having other tankmates.
I understand your interest in puffers, same reason I got into saltwater.
I'd love to have more than one too or even a large enough tank to house a dogface or a porcupine. That'll be a while though.
I'll be adding a Papuan puffer to my tank in the next month, hopefully.