I have kept many porcupine puffers and they are my favorite fish. I even have boxfish, they are related to them. I have always feed all my fish everyday and they have lived for many years. Maybe the lady at the LFS didn't have alot of experience in marine fish. If you read some of the marine fish books they say to feed your fish 1-3 times a day. But I would never feed them three times. As for there shape changing if you feed them to much if, its just not so. If you feed them alot there smocth does a little big but goes down in a few hours. And I have never heard of someone saying, feed your puffer greens, puffers are meat eaters, they probaply would not even toch greens. I feed mine, Brine shimp, Squid(they love it), Krill, Silversids. And I also soke all my food in a milti-vitamin liqid. That makes there emun-system stronger and less prone to get sick.