Mandarins are incredibly beautiful. However, they seem to often be sick or two to three days away from death by the time they get to the lfs. If you get one I would suggest getting one from someone that has had them spawn like letysjim and make sure you don't have any other fish like hawkfish or other gobies that are eating your copepods. You probably only want one in your 55 gallon otherwise you wont have enough copepods and amphipods. Sometimes you can buy a tank raised mandarin that eats bloodworms or brine shrimp, that is another way to go. Anyways, the best of luck. Don't get a diamond goby, they will knock down rocks and overstir your sandbed.