Hi, If you really want a mandarin fish, I would go to florida-aqua-farms.com and get yourself a large quantity of amphipods to place in your tank. I would try to buy at least a hundred of these....more if you can afford it. If you have a sump, try to place some in there and feed them some sinking alge waffers. I grew a culture once in a ten gallon tank to feed some seahorses once. They reproduce well, but very slowly. If you put all of them in the tank they may be all eaten before they reproduce in a large enough number. Live brine shrimp can also be used to suppliment the diet, but I have read that they do not contain all the fatty acids necessary to keep them healthy as a sole diet. I have always wanted a mandarin, but have not purchased one because of their dietary needs. I have read that these guys will not take non-living food, but I could be wrong. Do mandarins eat algae too? All I know is what I have read about these beautiful fish.
Good luck, Lesley