Honestly, you could go through many mandarins before finding one that will take to frozen food. I do not think you could meet a mandarin's feeding requirements with that small of a tank. Also, that's great that Legoalie's mandarin is eating brine shrimp, but brine has little to no nutritional value -- I wouldn't recommend feeding it regularly, or in place of other foods. Cruise through the old posts here with the search engine, and you will see that this situation will most likely not work. The mandarin will simply starve to death -- which is very sad thing to see indeed, for such a beautiful fish.