Max size of the SAP (Colomesus asellus) is 3: http://www.**************.com/forum/ug.php/v/PufferPedia/Freshwater/C_Asellus/
http://www.**************.com/forum/library/puffers-in-focus/sap/
http://www.**************.com/forum/library/hospital/dentistry/
There is a similar-looking puffer, called the Parrot puffer (Colomesus psittacus), which is brackish & grows to 15".