Ok, I'm jumping in. There is a good website called "[www].dwarfpuffers[.com] that is solely devoted to the care of dwarfpuffers. You should visit there. They also have a forum for dp keepers. I've kept dps for a couple of years and just recently started breeding them (not very well, too busy to spend hours looking for eggs or newborns). In general, dps are territorial. The mantra is "LOTS of plants and decorations that will block their line of sight" so if a hassled dp can quickly swim round a log or pot or something to an aggressive dp might not see him. Juvvie dps do seem to get along pretty well and will school but once they start maturing and their hormones get going, the dominant male will single out his choice female and fight all the rest--sometimes to the point of killing the others. Also, a pair that have been nicely breeding might all of a sudden fight (folks have found a dead female or a dead male with chunks taken out of it) for no apparent reason and up to then they seemed to get along so nicely. I had 3 in a 10 gal. tank heavily planted with logs and all, and when they matured, the alpha male chased the other male so constantly (and even chased the female but she didnt' seem to want him so wasn't cooperating) that I had to remove him to a separate tank. The "3 gal/dwarf puffer" rule is because they are scaleless fish so they are more susceptible to tank conditions and they are real messy (finicky) eaters--they'll watch their food drop down to the floor then refuse to eat anything that's on the floor or they'll grab one worm and the rest will drop and they ignor the dropped ones, or they just dont' like what you're feeding them AND because they are so territorial. So you have to remove the leftovers before they start fouling the tank (and if you're like me and rush off to work as soon as the fish are fed, the leftovers don't get removed immediately). From comparing notes of other dp keepers, we've decided that dps' teeth don't grow fast enough to really need to be ground down--bloodworms have a slightly hard outer shell that seems to be enough to keep dps teeth in good shape (daphnia also--soft inside with a crunchy outer shell, yum). Basically, dps love snails but don't generally crush the shells--they hunt down the snails (which is fun to watch--like cats do) and bit the soft fleshy parts until the snail dies. If it's a large snail and they can't eat it all, the dead snail rots so you have to remove it (and the blasted empty snail shells clog up siphons, o joy). Snails are not absolutely necessary for dp but they seem to love them and it gives them something to do (hunting the wily snails). If you have 2 males (at least one of which is mature), he will not tolerate ANY other male dp in the tank and will hound, and maim or kill, the other male (even if the other male is immature still). Females usually (note: "usually") get along ok together although they too can become aggressive with each other. Females will also attack males and males will attack females for no apparent reason. So give them a lot of space and plants and things to break up their space.
Well, after spending a considerable amount of time researching, I set up my own little five gallon up here at college and have introduced five Dwarf Puffers into the family! (The "family" consists of eight bettas and three goldfish.) Here's a picture of the little buggers: 
I plan on eventually adding live plants as a slow process. We have code names for their formations. So far, the favorite is that when there is a single puffer off on his own in a corner somewhere, we call him "The Assasain" 
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Haha. ...Have fun with your fish!
