You can go with two SA Puffers. They are small enough and should do just fine in a 10gal. If you do decided on these guys something to keep in mind is that they need a visually stimulating tank as they are very intellegent and will get bored quickly. You will need to be sure to provide them with snails so they get used to keeping thier teeth ground down. If not you will need to trim their teeth to keep them short so they don't starve. They are great fish to interact with and watch, I have 4 of them. I have found that they are happiest with a buddy so be sure to pick up two. They are not that cheap of a fish, from purchasing them (about $17per fish) to feeding them. Mine love frozen blood worms and crazy enough one loves flakes!!! Go figure they are interesting little guys.