www.dwarfpuffers.com will answer pretty much all of your questions. 50% water changes b/c they are messy fish, i feed mine frozen blood worms and then frozen brine shrimp as a treat once a week, they like a heavily planted tank b/c they are territorial and it helps break up their lines of sight, and you could put 2-3 in a 10g, maybe 4, but 3g per fish is what i have heard to go by. also they should be in a species tank, which means only other dwarf puffers, so if you want to add them to a tank already with fish in it then i would think about getting another fish.