Generally speaking the Atlantic blue will get around 9" fully grown, so a large tank long term is best. 180 gallon or bigger, 6ft long.
They, like other tangs will eat meaty foods, flake and pellets, but need algae in their diet on a regular basis. So, dry nori algae sheets placed in a algae clip provided a couple times a week will do.
If this is your only tang, introducing another tang latter will end up in a fight, possibly death to the new comer.
It's best to add tangs in multiples at the same time and they should be the last fish added.