Welcome to MFK!
Feed it live fish for awhile until it starts having some meat, you don't want it to die from starvation. Once he knows u bring the food, he will always expect it. So instead of live fish, u can start with frozen smelt, or Freeze Dried Krill, which is not cheap.
Do you know or have picture of your fish?
I have a 6-8" Indo Pacific Tarpon, with a 10-12 inch Fei Feng (Red tail Prochilodus), and they are OK in there. I just hope I could keep it alive to see how big I can get it to. Somewhere down the line, you might need to find it a bigger home, either get a bigger tank, or maybe sell it here and see if someone could buy it from you. I like to sometimes buy the fish already BIG, less waiting time for growing them.
Just enjoy your fish while you're here, and see if you can take some pictures and post it here

Again welcome, and don't be alarmed, enjoy your fish and hope it get's to the size you want it to be...
