I do keep him alone in his 6. I've read so many conflicting sites. Some say they can live together in a species only tank as long as each puffer has five gallons. Some say they should be all alone.
I feed him frozen bloodworms daily, 5 or 6. He eats until he can't eat anymore, literally he'll spit them back out when he's full. He eats them straight from the tweezers just like my bettas. Sometimes (like today) I throw 6 or 7 small pond snails in with him. They are voracious and they have an incredible metabolism. His fins move so fast they're a blur. He can see very well. In fact, he can see me coming with the camera from across the room and he hides.
My husband named him Huey cause he looks like a helicopter. We were calling him Nugget when I first got him because he was only about a 1/4 inch, if that. I had to put a mesh bag over the filter, he was so tiny. Here's a lil movie. Gosh he was small.
I think I'll have had him a year in March? He's never had a single health issue. Never missed a meal.
You should totally get the dwarfs. They BURST with personality and they're as smart as my bettas. I'm in love with a Porcupine puffer at my LFS but I don't have room for a tank that big in my 2 bedroom townhouse. LOL!