No. I've known people who have tried it and tell me "My fish are fine in fresh water" and a few years later thier dead. GSP's can live over 10 years and have heard of some living as long a 15. For a full healthy life they must have brackish and eventually full marine conditions.
A GSP cannot live its long life in full freshwater conditions eventually they will need a high brackish-full marine tank. Thought they can be kept in freshwater up until they are about 3 inches long.
a little salt like a teaspoon per gallon is good for a young age then at about 3 inches id up it slowly to full marine. Im in the process of acclimating mine. hes almost at 1.024.