blowing up of a puffer is one of the worst things that it can do not only does it cause great stress on them but if any air is inhaled while doing it they cant expel the air and definitly die. they dont normally puff up unless threatened or frightend
Puffers/boxfishes/trunkfishes can also produce toxins into the water when they are under stress, which can kill tankmates. Research carefully before buying these animals! Never encourage them to puff up!
wolfie