getting a mandarin to eat

[George]

Sorry about the loss.
Also remember that these fish don't come directly from the ocean to our tanks. They go from the ocean to divers to collection stations to distributors to wholesalers to stores. There maybe even multiple stops within each layers (like a store also wholesales live stock and sells to other stores). I don't think many of these places feed the fish or make sure the fish eat. We don't know how long the fish has left the ocean and in transit.
The best advice I can give is that the old recommendation of seeing a fish eating in the store is still a golden recommendation. As long as you are not looking for a super rare fish, the same type of fish will show up sooner or later. Buy the fish that is eating in the store.