As you may have seen from the other comments, some puffers are aggressive while others don't seem to be a problem. I saw a puffer in the store one day and decided I had to have one. I began the tank with one spotted puffer and two bumble bee gobies. I then upgraded to a 100 liter tank that now contains three gobies, three orange chromides, three archer fish and two black fin shark catfish. Oh yeah, there is a clown pleco in there too, but he never comes out from the back side of a piece of driftwood so he doesn't really count. Anyway, my comment is that all of these fish (at least the particular ones I have) get along great together. The only problem is that sometimes the puffer will bite at the catfishes' dorsal fins, but he never even chases any other the fish around at all. I keep them all well feed with frozen brine shrimp, crickets for the archers (which the puffer and chromides like to munch on as well), and occasion snails from a different tank to keep the puffer's teeth ground down.
These fish are very agressive. I had a 4 cm specimen in a 200 L with a Red Belly Pacu about 20 cm long and various other fish. After the first night the Pacu's fins looked like swiss cheese because of this little guy. These fish can be kept in fresh, brackish and salt water. But they are very susceptible to fungus in total fresh water. I eventually moved mine to its own tank where I also witnessed the funny shimp hunting where it would turn its back and wait until the shrimp wasn't looking. I also witness the jumping and biting. We had a table lamp behind the puffer's tank and when we reached to turn on the lamp it would jump out and bite us on the arm. He never got full. He would gorge himself until his stomach had blown so big it doubled his size. Then the next morning it would be gone. Very fun fish. Can be kept in a larger tank with monos and scats when it gets older.
Having recently moved to China for work, we purchased a beautiful 450 L aquarium and were excited to find "cute little " puffer fish at the market. We added two "docile" puffers to our existing mix of angels barbs and tetras. We quickly discovered that these comical fish are coy and vicious. They will lie in wait for a passing fish and with an incredible burst of speed take a large bite out of the unsuspecting passerby. Needless to say, it looks like we will be adding a second aquarium for puffer habitat.
Fin nippers? Try fish eaters. When I first got my puffers, they ate some of my original fish while I went away for Spring Break. But now that I've had one for about six months and got him a tankmate of a Figure Eight Puffer, they are much more calm and in fact, did not eat the two feeder fish I put in recently. They like to "pout" and sit at the bottom of the tank and they also change colors. I love my puffers and anyone can own them - just remember: they're BRACKISH!
I love my Puffer. Keep them well fed or you will regret it. I feed him shrimp pellets mostly, but I do keep small guppys in the tank to curb his "fresh meat"habbits. If you must have other fish make sure their fast and aware!
I just wanted to add that green spotted puffers have poison as a defense mechanism against other predatory fish. I say this because seconds after I introduced my puffer into my tank, my oscar bit the puffer on its side and after approximately 30-60 seconds my oscar became stiff, tumbling and turning at the water currents will. I thought my oscar was dead, but then I noticed that it twitched every few minutes. Little by little my oscar regained his balance and after 2 days he was able to moderately swim and eat a little food. I really thought he was a goner though. Needless to say, I moved the puffer to another tank.