Mike, I would stay away from the goldfish, they offer little to non nutritional value and as feeder fish, they dont receive the best care at the pet shop. I tried when i first got my puffer, and although i have never been able to figure out what it was exactly, i believe my puffer got sick from it. I know they say most diseases wont survive once in salt water, but in my experience i have doubts. The reason because the last time i got goldfish, the puffer eat it, no problem. I went back the next day for some more and 100% of the feeder fish had died overnight, the store would not tell me why. Within a few days my puffer stopped eating, developed Ick and some type of skin fungus. Had to treat him for almost a month with paraguard, i didnt think he would make it, thankfully he did. But it wasnt pretty. If you want to try a fish spend a few bucks for a guppy or molly, even a zebra, they are cared for better than the feeder fish, but i would do that as a last resort. I would try feeder shrimps before fish.