I used to feed my puffers feeder guppies. They would hunt them down and rip them to shreds. So, they do eat other fish, not just nip. But then again, I keep my puffers with rainbowfish and little gobies right now, and they don't even look at them as food. I've also kept them with fancy tail guppies and swordtails. None of them were eaten either, not even nipped. It just depends on what kind of fish you are putting in the tank. Be smart about it. Put yourself in the puffers shoes (or fins) and ask, "Would I eat that?" Keep a few ghost shrimp or snails in your tank at all times and the puffers should be able to eat those when they are hungry, rather than chasing down other fish. The best bet for community puffers are dwarf puffers, green spotted puffers, or figure-eight puffers. The younger they are the better. I also think another part of keeping puffers from nipping other fish is to keep the water at their preferences (GSPs and F8s like brackish, alkaline, warm water, not 100% sure about dwarfs.) Also having a tank with lots of stuff to explore for them is crutial, because they are very intelligent and once they get bored, they start looking at other fish as toys.
