I have 2 dwarf puffers in a 20 High tank with 14 other tetras, a dwarf frog, and shrimp. They're perfectly amicable with the other inhabitants. Actually, it's my tetras that are the aggressive ones. Usually between themselves, but they'll go after a shrimp or puffer every now and then, just for a moment.
I think the understanding of puffers as being aggressive is commonly considered universal, when in reality it might only happen ever now and then. They're fascinating fish, with actual personalities, some are shy some are aggressive. One seems to be horrified by me and always freaks out when I look in the tank, while the other just passively chills. I love these fish.