Any info on how to care for a Leopard Puffer?

I'm looking to get a Leopard Puffer from a pet store within the next few days. From what I'm hearing and reading they do best in brackish water. Can anyone please tell me exactly how much sea salt you need to add per gallon? Also, what do they eat? Do they need any other special requirements? I would like to know as much as I possibly can before I bring him home so any and all info is appreciated. Thanks! :)