Porcupine Puffer Emergency!!!

Puffers are smart fish. What you can start to do is feed the live shrimp using tweezers. Don't just drop the shrimp in, make the puffer take the shrimp out of the tweezers. The puffer will come to associate the tweezers with food. Once you've been using the tweezers for a time and the puffer goes into food mode when it sees them, try feeding dead ghost shrimp. Once it takes the dead shrimp regularly, try a new food.

Although I still feed frozen food, I've been able to get my puffers to accept freeze-dried food using this method (which will come in handy when I go on vacation and need to use an auto feeder).

You may try seeing if he will take them with a drop of garlic on them. Then once he is use to that try putting a drop of garlic on the other foods so he will associate them with eating.

When I first brought my puffer home, he had been raised on feeder guppies and I had a hard time getting him to eat anything else like you. I eventually just stopped feeding him and since they are big eaters, he eventually took to thawed out frozen Krill. I bought myself a tool used for FW planted tanks to trim and move plants and just pinched some krill in the 'fingers' of the tool and brought the food to the puffer. It only took a couple of days until he was apparently in love with the krill and I never had any problems again. I did eventually trade him in though since I want to change my tank into a reef.

The only caution I would have to point out is that puffers cannot really be trusted with other, smaller fish. Mine was great at killing four clownfish and three green chromis. I bring this up because you may not want to starve it for a day if there are fish that it can substitute for dinner that you would like to keep.