Get 2 of the arrowhead puffers. You'll have more fun with those guys. I had four in a 55. Only the puffers in the tank! Anything ele would be uncivilized/ HA HA HA.
I would suggest one per 3 to 5 gallons at the max, and thats long term, Also it depends on if you plan on having other fish, or what kind of ornaments or plants you have
You'll want 3 puffers and 3 bumblee gobies. BTW, Dwarfs is the correct spelling-- little known fact... JRR Tolkien created the plural "dwarves" for the Hobbit because the proper plural, "dwarfs", didn't befit the pride and nobility of the race. Keeping multiple puffers requires very good decoration to prevent one from chasing the others mercilessly around the tank. In a 12, fake plants will do-- live if you can grow them. No large ornaments, though, as you need all the water you can get circulating in such a small system.
A figure-8 puffer is perfect for a 12-gallon tank. Add a teaspoon of salt per gallon, put in a couple YoYo botias, and sprinkle Malaysian trumpet snails to taste. When the YoYos get 3-4", sell them for a profit and buy a couple more. Rinse, lather, and repeat.
Violet gobies are unbelievable bottom feeders, and sift through the sand to pick up excess food. We got ours at about 3" and grew it out to 7" in an 18 tall (same footprint as a 10) for about a 8-10 months-- they need at least 1.003 and they need more space in the future. I don't recommend a tank less than 20 gallons long term for any fish, as larger systems are more stable. A 30 gallon would look great with a figure 8, a violet goby, a couple black mollies to eat algae, and a handful of knight gobies (bumblebees if that's more your thing). More fish waste, but no leftover food decaying, so it balances out.
