That looks like a Tetraodon sabahensis to me, they do require a little salt in the water. I have read they are quite aggressive as well so I would not risk putting anything else in the tank as it will be seen as food.
There is a local Fish shop by me that has two for sale a good 9 inches in lengh, but they are in a very sorry state I was tempted to get one but I don't think they will last.
The shop has them in full marine conditions but they are not doing too well. They had them listed as Giant Puffers, had no idea where they came from, what their latin names were or how to keep one. Apparently they sold a third to a man with a Red Tailed catfish....oh dear
Do you mind me asking where you got that one from?