Those smaller puffers do need regular dentistry. Nile puffers teeth don't grow that fast so only occasionally need crunchy food. That said, I do like to feed cockle in shell to the larger puffers just to enjoy the strength of their bite!
Alright, with the teeth issue. If I were to put just the shell from a dead snai in my tankl, would the puffer use this as an aid to trim down his beak on his own? Or would this beak trimming only work in the process of eating harder foods?
Use live snails as an incentive to break them open. Otherwise buy cockle in the shell and stamp on them to break up the shell - that way the puffer will have to pick through the bits of shell to get the meat.