Well, put it this way, if the fish you are feeding the puffer doesn't exist in its natural environment, it's probably not a good idea to introduce them to the puffer.
55G is tiny for the puffer. You'll see. That cute little puffer will become a gargantuan puffer in a matter of months. By that time, you'll probably be too attached to donate it (in case you have no time or what not to upgrade to 180G). I am just speaking out of experience, by the way. But I did have to donate the cute one to the LFS
. I still see it in the LFS
whenever I visit which is almost every week.
Hope you have excellent filtration because eventually they will poop amazingly sized feces all over your tank.
When you said the biggest reason you got the puffer is because it eats gold fish, I hope you are kidding. There must be a bigger, more important reason than that.