It is a predator tank, as stated in the first post. A SW predator tank means no corals, no inverts, no small community fish. Puffers will eat snails and crabs, actually, they have to eat crustations to grind their front tooth down. If they don't, the tooth will get so big it will cause the fish not to be able to open its mouth wide enough to eat. Regular feeding of krill, squid, clams, and teeth filing hard-shell shrimp is suggested to help keep the puffer's teeth groomed. When I had a porcupine puffer I would usually buy about 10 snails a month for the puffer to eat. That is the reality of a predator tank.. there will be death involved.
While it is true that it is not good to feed the puffer FW feeders, that doesn't mean don't do it at all. If that is what is required to get it to eat in the short term while you ween it off to other foods I would still do it. Just do it sparingly, use something like a molly fry or guppies. I wouldn't do it for more than a month and I would do one small live FW feeder then use a feeding stick with fresh seafood to see if you can ween it to other foods.