I have a porcupine puffer that i have had since he was about 1.5" long and he is now about 7", i noticed last night that he was fully expanded "puffed up" this is the first time i have ever seen him do this. I honestly dont believe anything startled him due to the fact he is the biggest fish in the tank, i have noticed now that he is breathing a little heavy not to a concerning extent and he is acting real lazy compared to his normal swimming around the tank, he is still eating normally but my reason for concern is that i have never seen him act this way...is there something wrong with him possibly? Or is this normal behavior after they expand themselves? Also do the expand themselves every so often because they are growing?