Spotted Pufferfish question

Question
My daughter had a beta that recently died. To make her feel better I promised to eventually buy her some new fish on down the road. Well, she got to choose her fish on Wednesday. She chose a weird looking goldfish, two Mollies, a tiger bard, , there were three tetras but they were eaten. Along with this eclectic selection she chose a spotted puffer fish. He was doing great up until today. I have added what I have which is frozen blood worms, and Tetra tropical flakes. I read that the Puffer fish requires shell fish. Is there any other way for me to feed him what he needs without causing snails to infest the tank that I have? His fins were a little damaged when I bought him, but they seemed to have healed. I worry because today when he swims, he kind of wobbles from side to side, but his little fins are still going ninety to nothing. I really don't want him to die, for one he's my daughter's favorite, and he's the only one I like. I've tried to call local pet stores, but "it's against their policy to discuss anything animal related over the phone". I am really frustrated, please save me from having to get rid of the little thing. I really don't want my daughter to get upset.....again. Thanks in advance for any help you may be able to give.

Answer
Hi Ariana:  Your issue is complex... because you have mixed goldfish with tropical fish... goldfish are coldwater fish and tropical fish need warmer water then goldfish can tolerate.  To treat the puffer you will need to raise the tank temperature to about 82 degrees, add aquarium salt per its instruction label.... keep me posted on his progress:

ok... snails... the way to deal with snails is for them to have their own tank or container... you put one or two in the tank at a time and the puffer will eat them or not... do not add more to the tank until he eats the ones you put in... this way you keep a snail supply on hand that is not over running your tank... dave