Thats a completly seperate population though. Tarpon are saltwater fish and that is just a population of them that have evolved to live in freshwater. It could work, but i think saltwater would be better in the long run.
I have a trio of indo-pac tarpons in my 650 with a shoal of 5 IP mullet. Very active tank except for the FL gars and tropical gar at the surface. My 16" af aro lines up with them when they cruise as a group around the tank.