I made sure mine ate frozen in the LFS before I pulled the trigger, but when I put him/her in the tank, it was a lost cause since other fish ate the food too quickly.
Over time I developed this following routine
1. thawed a cube of brine and a cube of mysis in a small container with tank water. Mysis can be too big and brine is not as nutritious. I also at times add Reef Nutrition R.O.E as the Mandarin gobbles them up.
2. I turn off all pumps (this is programmed into my apex feed cycle)
3. I note the location of the mandarin
4. The fish recognize when I have my Julius Thing ( reef tank turkey baster) and circle at the top of the tank where I then dose two good squirts of food to start the frenzy
5. I feed the cleaner shrimp directing it away from the mandarin and my nem
6. I then squirt the mandarin
7. I quick squirt at the top to decoy the fish again
8. I spot feed the nem
9. I dump and rinse the container into the tank
10. The mandarin can pick off the food on the bottom for 20 minutes while all pumps are off
11. The DT pumps come on after 20 minutes to kick food as much as possible in to suspension for the coral. The clowns and chromis continue to feed the water column aggressively.
12. 10 minutes later the sump pumps come back on to remove any uneaten food.
This routine has turned into a mandarin life saver as I had to rip clean my tank and am not able to re-establish pod colonies yet. Absent of the pods, the mandarin has been feeding a lot more aggressively to my relief and surprise. I would say it was. fairly passive eater at feeding time, but once the pods were gone, it got a sense of urgency and now goes to town as soon as the dousing of shrimp arrives.
He/she is doing well and appropriately fat, but not an ideal situation since they really need to a eat small bits all day