okay soooo i can see first off that the chunks are too big. 1in is much bigger than their small mouth opening. my shark right now at about a month old has a 1/4 in mouth opening, which means their throat is even smaller. Try going with tiny tiny pieces because that way they will be more apt to eat. Bamboos are sorta hard to get to eat in the first place, some sharks are really picky eaters. mine took a liking to silversides and squid. it could also bee that your shark is lacking iodine which is a thing they will need later on.... Try soaking the food bits in garlic extract and then feed it as much as you can get him to eat without over feeding (don't wanna go from starving to gouging it).
have you ever tried handling your shark? I know most people would say thats something to never do since they are a "wild animal" but since its my major (marine bio) and i use my tank for home research (or at least thats how it started ;D LOL) i have handled mine from day one.
have you ever used copper in your tank? what are the levels, temp, and salinty of your tank... sharks require everything to be a bit higher, and how much flow do you have goin' on in your tank? give us some info man!! LOL :D post a pic of this lil dude! I wanna seeee :)
and heres a myth buster for you... even tho thse are wild animals it doesn't mean they are going to be more "alive" at night, yes sharks are nocturnal but not to the extent that people believe... these lil sharks tend to be out and about all throughout the day, not just at night... plus how long did you have him from an egg? at the aquarium we've seen that sharks who have their lights on for the normal daylight time and then off at night tended to go to "sleep" when all the other fish, where as the sharks with the lights off in the day and on in the night time would react different, it was up during both times with little resting periods