If he is laying on the ground everything is ok. my grouper always lays with his tail curved. most puffers are lazy like that and always curve their tales when they lay. if it is crooked when he is swimming it my have a break or infection in it. Or he may be doing this just to do it. are there any bad signs? later, bo
Don't worry. I've had a dog faced puffer 7 months now and that is normal for them. They use their tail for a rudder most of the time and only use it for propulsion when they need to move fast. You will notice when they swim that they will curl if from right to left to change directions and will leave it in the last position they used to turn.