There are captive bred specimens out there that have been raised on frozen food from day one, and have no problems eating dissolved cubes of brine/mysis shrimp and going along the bottom picking at things they find. I've had mine since I first started stocking my tank 6 months ago, and he's an adult captive bred male and does great, eats frozen food no problem. Many of the specialty fish stores make a point to carry captive bred fish whenever possible, especially when it comes to mandarins. Well, the ones worth their salt do anyway.
My one suggestion though is that if you get one, plan to target feed it with a turkey baster, commercial target feeder tool, or something similar. They are VERY slow, peaceful fish and 90% of the time they will get beat out by other fish in the tank when going for a bit of food. They tend to move in slow, jerky movements like a bird (imagine a robin's head as they listen for worms underground), and will stare at a piece of floating mysis shrimp from 10 different angles before moving forward to eat it. Half the times mine is so slow getting to a bit of food that the flow in the tank carries it away before he even finishes approaches it. It's easier to ensure they're getting enough food by sucking up a bunch of food into a target feeder then squirting it right in front of them in a corner or other low-flow area (after putting food out into the main tank to distract the other fish first). They tank a bit of effort, but are SO worth it in my opinion. He's easily the most beautiful fish in my my tank.