it will munch on seaweed or graze like most tangs but it is more of a meat eater so i would reccomend feeding it a variety of meaty foods like brine and mysis and where its so small you may want to use flake food or something small like cyclopeeze or baby brine whichever you can find.making your own is def a possibility but small food in small doses many times throughout the day as alot gets carried away with your wavemaker or powerhead and the fish is too scared to hunt it down.
garlic isnt a cure but will help entice the fish to eat....its like candy to them lol and if it wont eat then theres a good chance he will give in to the ich
cheers