Green Spotted Puffer acting Shy and doesn't Say Hello when I come up to the Tank.?

I got a Green Spotted Puffer probably about 4 days ago. At the moment he is in a freshwater tank because he is only about an inch and a half, he is with all of my community fish. I have read A LOT about these puffers, I made sure I knew what I was getting into before getting one. I want to upgrade to something a little harder than a freshwater, so I'm going brackish. Anyway, aren't these guys suppose to be aggressive and fin nippers, and aren't they suppose to come say hi when someone walks up to the tank? My little guy backs away and will sometimes hide when I come up to the tank. He is very friendly with my community fish and has never tried to nip anyone. He is very inquisitive and checks out his aquarium and will swim around and act like a normal puffer in that sense, and he has a nice round belly and I keep his well fed, and I give him snails to ensure his teeth don't get too long. As I said before I know how to care for these guys, but he is more shy and friendly than aggressive. Is this normal for a young one, will he grow into his aggressiveness? If he doesn't than that would be nice as he could have tank mates. At the pet store I got him from he actually got picked on by the other puffers in the tank, if that makes a difference at all.