I think that one would be ok in your 5 gal. However they are messy eaters, as in half the food I turkey baste to mine actually make it to their mouths, and the other half settles to the bottom. The moral of the story is, make sure you keep up with your water changes, because no one wants a smelly tank.
Also if it's possible for you I'd recommend going for a bigger tank size so you could stick at least a couple in. It's fun to watch them chase each other, or when they get scared by something they all huddle up in a group. And swim around the tank as if they're trying to re-assert that they own it. Be careful what you put in with them though, they can be mean. So far my amano shrimp have mostly been left alone. I had an oto cat, but it died, although I don't think that was from the puffers. The link in the above post really is great, especially the forum. One more note on dwarf puffers, they do not eat flakes. Or sinking tablets. Mine only eat frozen bloodworms. I haven't as of yet tried live food though. :devil:
