Ed they do do well in a higher spg . Most brackish can go full marine but I do not know if they stay there , as some species do . Some are born in the estuaries and when they grow go to the ocean as adults some do not , some stay in the estuaries as brackish ...... we had green spotted puffers they were bought in total fresh water as they grew they went brackish , and then to marine when they were traded out they went to the marine tanks of the store , where they thrived for a few weeks before being sold . Many times they can go full marine however there are species that do not . As I said I am not real well versed in brackish species but have some experience with them as I did keep them for a period HTH :mrgreen:
One other thing not to sound harsh there are NO guarantees in anything we do they could die be it in fresh or salt or brackish