How to avoid lock jaw in puffer fish?

i have a porcupine puffer in my 110 gallon tank. i have had him for about 10 months and i have been meaning to post this question for a while now. he does not have lock jaw at the moment and i want to make sure he never gets it. i am worried about it because all he will eat is frozen krill which is what many people believe to cause the problem. i have tried tons of other foods with him like squid, silver sides and clams but he has no interest in anything besides krill even if i use garlic which tends to work with my other fish. recently i have been hiding bits of silver sides in the krill which works if he doesnt realize what he is eating but he is still getting the krill also. i want to get him completely off the krill but im not sure how to go about doing so. thank you for any ideas!