Many brackishwater fish can survive for extended periods of time in freshwater, but it's not good for them. It compromises their immune system and puts them under unnecessary stress which in the end greatly reduces their longevity. Without knowing which puffer species your talking about for sure it's hard to give you appropriate advice. I'd add the scientific name so we can be sure of the id of the fish in question. Though assuming your talking about the same green spotted puffer I'm thinking of they're brackishwater fish not saltwater nor freshwater, so they should appropriately be housed in a brackishwater set-up. There are some pure freshwater puffers out there though Congo's, Hairy, Arrow Head, Pea, Mbu's and Fhaka's. By the way I like the username you chose would've been perfect if it was Puff, Puffer Pbass though.lol!
