Tang police! :D
Anyway, brine is like candy to fish -- very little nutritional value. Stick to algae sheets clipped to the glass, or rubberbanded to a piece of live rock for them to graze on. Maybe yours will also eat spirulina and mysis.
But watch out for ich. In a 29g, if you did not treat for ich before putting him in and if you already have ich in the tank, your tang will catch it if it's stressed.