(thread was moved from for sale forum)
You will want to buy copepods for the fish, BUT once a Mandarin begins to starve, they too often do not resume eating and starve to death, so time is of the essence in this case.
Your tank is fairly new IIRC, best for you to get him into an established tank (min 1-2 years old with lots of rock in it) ASAP. It will be very difficult for you to purchase enough copepods to keep him fed - as it is said they eat 200-400 of them per DAY.
Local to you - you can probably buy them at either Total Aquariums in Lynbrook, Mutts & Butts in Merrick or Pets Warehouse in Copaigue..call first to see if they have them, but I still stand bu getting him into another tank asap.