the 29 is what i am saying is to small for them. i am not trying to offend anyone or bash anyone for anything, just looking out for the well being of the fish. a small tank will likely cause stress to them and stress can cause all kinds of other unwanted problems with the tank. these fish can reach lengths of 10" - 11" in captivity (i have seen them) ...
The Porcupine Puffer - Diodon nicthemerus
this one is at a friends house and is over 12" long ... granted it is an old fish, but ...
that is all i am going to say about this.
