it might be worth trying some live food with him. freshly hatched baby brine shrimp nauplii, black worms, white worms. sometimes live food can pique their interest.
it might also be worth picking up a bottle of Selcon. i've seen an increased feeding response in all my fish when the food is soaked in Selcon. it stinks to high heaven, which is probably why.
in a related note, since your tank is so young, is your water quality in line? making sure you NH3/4, NO2, salinity, temperature, and alkalinity are in spec would be a good idea. problems in the environment can manifest themselves in many ways, a stressed fish is very likely a fish that is not prone to eat.