Yes and no. They love otocinclus catfish, actually pretty much ignore them. I keep my dwarf puffer with a Dwarf Crayfish. Nice little inverts. In a tank that size, I'd probably do a dwarf puffer. I keep mine in a 2.5. Also, a cool idea would be a half and half tank. You could fill in 2.5 gallons of water, and add a plexiglass divider in the middle and make the other half land then find a nice little amphibian that be compatible with the Dwarf Puffer. I've often thought about doing this with my 10 gallon, and it's just an idea, I've never actually had amphibians, except for my hermit crabs which I've had for 6 years now. Anyway, don't shoot me because I don't know about that lol. Just some ideas. Hope I helped!
Nils