Hey,
Tsk, tsk, tsk! Should have asked those questions BEFORE you got the fish. Now we need more info. What's in your tank now, how long has it been set up ect ect ect.
Manderin's mainly eat copepods and need lots of lr to graze off of. If there aren't a lot of aggressive feeders in your tank he/she may eat frozen brine and such if he/she can get at it. I don't know what your other fish are and what you're feeding them so I can't help much.
Take care,
Dan'l