How big is your tank?
How many pounds of LR
do you have?
How long has your tank been running?
Mandarins usually consume a vast number of copepods, amphipods, and other "pods
" daily. They are extremely difficult to wean onto frozen or processed foods, and many mandarins will never accept anything but live pods
. This is why they are considered expert level fish and are thought to best thrive in large, mature systems with copious live rock.
There are online retailers in the US that sell amphipods and copepods, but that gets expensive if you don't have a place for them to reproduce (refugium, large tank with a pod pile, etc.).
Can you still return it to the lfs
for store credit?