Yes and Yes, though that diet is not diverse enough as primary diet and it will be problematic. Don't feed them dry krill - be sure you soak for awhile, ideally using some liquid additives (like selcon) to boost the nutritional value. But overall you will need to feed them some hard shell (eg shell on) shrimp, as well as mussels, clams, etc. I would even keep some snails in the tank for him to enjoy. Overgrowth of teeth can be an issue for such puffers so they need their natural hard diet to help.