If puffers don't eat the shells, then why is it (reportedly) so important to give them shelled treats to keep their teeth ground down. I've heard that without snails (or another shelled snack) their teath continue to grow and actually can cause them trouble with eating by growing too large. Is this and urban (or rather aquatic) legend?
Also, how many do you guys believe will work in a 55 gallon with only FFF (flag fish) as tankmates? I have about 8 or 10 FFF currently, and expect them to breed. I don't mind some fry being eaten by the puffers if they are into that, but I don't want the tank to be an aggression problem either. The FFF are pretty quick and kinda territorial themselves, so I believe they may be able to handle themselves. If I want more fry to survive I could always set up a breeding tank!