I would definitely say that the chances of the Mandarin's survival are not very good. Are there enough (any?) pods in your tank? If there is not any pods in your tank, then, yes, your mandarin is in trouble. Some people have gotten them to take to brine shrimp, but that is not very good for their diet. If you can keep him alive on brine though, until the pods begin to accumulate, that would be okay, but I highly doubt that your young tank will be able to produce the pods at the level that he will want to eat them.