How can I stop my fiddler from eating my other fish in our aquarium?

In the wild fiddler are scavengers, eating bits of organic matter they find in the sand/mud. In captivity, they can be fed sinking crab food, fish food meant for scavengers (sinking tablets, shrimp pellets, etc), and freeze dried plankton and shrimp. so u need them to be separated! take a net and try to put then into a tank without fish....u need advice from a vet here's a website good luck!.........