I got this stars and stripes puffer from Tim about amonth or so ago-other than shelled animals, (snails, etc.) what can I feed him to keep his teeth filed down?? I really don't wanna gethim out and manually file them, but don't really wanna feed him anything alive either. I've been feeding whole (frozen) shrimp with the shell on (i'd heard that was sufficient for their teeth)-is that true?