I have had one puff before. Friend stuck her finger into the tank and poked it. It puffed up for a quick second and then went back to normal.
You can feed them bloodworms once the snail population is done. But with MTS I doubt they would go through them too fast. With pond snails I never see them without a bluge in their stomach.
They are the only fish I really like keeping because they have so much personality. They keep swimming around trying to look at me. When I sit on the couch to the right of the tank I always see them checking me out. That is why my puffer tank is in my living room and my rili and OEBT tank is in my office. They are so fun to interact with all the time.