Two puffers are commonly imported as green spotted puffers, Tetradon fluviatilis (Common Spotted Puffer [CSP]) and T. nigroviridis (Green Spotted Puffer [GSP]). You can tell difference typically fairly easy in the eyes. The CSP tends to have reddish eyes, whereas the GSP tends to have yellowish eyes. CSP = 6"-7". GSP = 5"-6". The two above mentioned puffers have similar water parameter requirements for salinity. Keeping these between 1.010 and 1.018 is ideal. Though these puffers do tolerate freshwater for a short amount of time, they tend to get stunted in growth and fall ill much easier. If they are in freshwater now, I recommend starting to increase the salinity in small increments immediately. Just a side note, they tend to be sensitive to nitrogenous wastes. I just compiled this info from a couple of books on keeping brackish fish, as I do not have a whole lot of experience with puffers because mine's unrelenting and waspish attitude.