Different puffers require diff water param. If you are after a larger puffer try getting a Fahaka puffer (Tetraodon lineatus) grows to around 20 - 30 cm and in wild about 40cm. This puffer is fine in fresh water you just have to make sure you keep the water hard, about 10 dKH.
I got mine down here in Chch at organism, just a little exspensive though. Theyre selling them now for $80!