When I buy fresh seafood, I bring it home a freeze it before feeding it to my puffers. When I'm ready to feed I defrost it in tank water, add vitamins and feed.
How I feed:
Crab: Take it home pull the legs and pinchers off and cut the bodies into 4 pieces, feed one piece at a time, then freeze in a ziploc bag for future feeding.
Clams and Mussel: For larger puffers, open the shell and drop one in there. For smaller puffers do as marksrush said.
Shrimp: For larger puffers feed the whole shrimp with shell on. For smaller puffers I cut into pieces.
Earthworms: Rinse well then feed.
Before buying a whole bunch of food at once. I bought 2 mussel's, 2 clams and one crab. I brought it home to feed to my puffers. I wanted to make sure they would eat it before I came home with a pound of something they didn't like. I'm about to try scallops and a few other things I saw at the seafood department yesterday. If your puffer is 3" you can feed him/her a whole mussel (they don't have much meat), or 1/2 clam (seems to have more meat).
