I, too, bought a Mata w/o knowing for sure what I bought. It took him a year or less to make it to 12" and now he's my favorite fish in the tank. He'll take nori or shrimp from my fingers and has never mistaken my fingers for additional pieces of food. When I use a hand scrapper to remove algae from tank he'll stay close to my hand (frequently bumping me) so he can swallow the next piece of algae as it comes off the blade.
His tankmates include six other Tangs (1 purple, 3 Hippos, 1 Scopas, 1 Yellow) and he's never started any fuss.