I am not sure where people are getting their information from but brackish fish go between fresh and salt. They live in fresh as juveniles and go into brackish/salty as adults. They do not live in full salt as adults or you would find them sold as saltwater fish captured in adulthood. For those that don't know, brackish water is found when rivers run into oceans. It is semi-salty water. If you are going to convert a brackish puffer into saltwater then do it very slowly, as in months. You will need a conversion tank. It cannot be done in a matter of hours, unless you happen to get one puffer that will live through anything. When they are acclimated into salt, they do best at an SG of 1.015 but can live in 1.022. If you have a system containing inverts that need a higher SG, your happy medium will not be found. The inverts or the fish will die early.