Your tang needs to eat more? Your kidding right? I can't get my other fish any food until the tangs have finished eating
Mine are chubby little blokes that constantly forage for food.
To answer your question - they like all of it actually.
I use Formula one Flake food twice a day with a third meal of prepared frozen Green algae/brine shrimp.
My tangs never miss a meal (they eat anything with algae in it but all my fish prefer the Formula One Flake food over everything else I feed them including prepared frozen treats.)