Is this a question or a statement? I can't tell very well so I'm going with question.
When I was 13 or so I bought a green spotted puffer and put it in a 5gal with a couple guppies and a goldfish (I know, I was young a stupid). To say the least, the starving little puffer ate the two guppies and then ate all but the head of the goldfish. I was very shocked but looking back I'm not surprised at all, if only I knew what I did today.
Puffers are natural predators, anything that moves is fair game for a hungry puffer. Similarly sized fish are probably safe if the puffer is well fed. Small schooling species may be safe if the puffer is too big to bother going after tiny morsels, unless it's hungry. The main thing to remember is they are predators and they need at least brackish water. Mollies and guppies, if you are not too concerned about some getting eaten, are a possible option for tank mates. You could pretty easily have a tank full of breeding livebearers as a constant supply of food, that is only if the puffer tolerates the adults.