Dwarf Puffers only eat live or frozen foods like Bloodworms or shrimp, and must be fed snails regularly to keep their teeth (bony plates that constsntly grow) ground down (I feed my 6 pack about 15-20 a month now). There have beeen reports of some eating flakes, but that is very rare.
I feed my little guys twice a day (some folks recomend every second day) because I find that their metabolism is quite high and if you skip a feeding they start to look sunken. A little in the morning and a little at night keeps them chubby (Ok Fat) and happy
The Dwarf Puffer is comfortable at all Ph levels, but they require a clean FULLY cycled tank as they are sensitive to poor water quality and can get sick very quickly. Most Dwarf Puffers are wild caught and many suffer from internal parasites. When picking out Dwarf Puffers look for a healtyh white belly that is at the least flat (not sunken) but preferably chubby. Don't worry too much if they aren't a nice green/gold color as their color changes with their mood...hehehe Mood Fish
There is no problem with sticking your hand in at cleaning time (as ling as it's clean) as their mouths are so small they might be able to grab a stray hair but I doubt if they could nip you. They will follow your hand around as they are very curious fish.
Here are some of the posts I babbled about my puffers in