As far as Puffer's growing teeth: you have to let them eat things that have hard shells; chewing on those grinds down their teeth. If you have snails/hermits in your tank, chances are the Puffer will make meals of those and grind down his teeth in the process of chewing their shells. Feeding them something like Krill or Prongs, with the shells on, will do the same. I wonder, too, if pellets have the same effect. Unless they're too softened by the water they need to be chewed as well.