GSPs aren't all bad. They all have different personalities, just like every other creature. Granted, they're more likely to be aggressive than some species. I've had one for about 4 months. He's in my 75 gal brackish along with 3 mollies, 1 dragon goby, 2 killis, 2 knight gobies, 4 fiddler crabs, 2 red claw crabs, and a figure 8 puffer. He gets along perfectly with everyone, even the crabs. I love puffers so I bought another GSP for the tank. this one was a holy terror! He chewed the fins off my killis and harrassed everybody so I had to put him in a seperate tank. The puffers loved eachother and were almost always side by side. Puffy seemed lonely after I took out his evil buddy so I got the figure 8. I've had him about 2 weeks and he's very mellow. I'd definitely keep a close eye on your tank when adding puffers, but there's good potential for a nice community fish.