Here how I got mine two mandarins to eat mysis shrimp. I put them into a smaller tank, like a 5 gals with some live rock. Buy live brine shrimp, use a turkey baster and slow squark it in front of the mandarin. When the mandarin inhale water, he will acciendently inhale in the brine shrimp. This will intiate him to eat the brine and then from there on you will be able to get him to mysis in no problem with the same method. My mandarins love mysis more than brine. Alot lot of people said keeping mandarin in small tank is not possible, but I have kept one for a year now in my 20gals and one for 4 months now in my 5 gals, they are doing fine.