I have had two dwarf puffers for almost a year now. A male and a female. I actually move them from tank to tank for snail control. Their man tank however is my Fluval flora tank, 7.9g. They live pretty peacefully in there with 1 pygmy cory, 3 scarlet badis and a bunch of cherry shrimp. I feed them frozen blood worms 2x a week, and the rest of the time they snack on snails. They don't go into my other puffers tank, but they do go into my 75 for snail control, and only end up spending a day or 2 in that tank as they really do a good job. They used to be quite skittish. but now they like to watch me wash dishes lol
They are really easy to take care of, although I think they are a bit fragile when they are little. They are very intelligent, and need a lot to look at, so a rather densely planted tank is good for them.