I agree with the guys above but I'd also ask if you test your water and what the results are. Is the tank cycled? If yes, how do you know?
Have you read their numerous profiles online? There is a lot of info out there that doesn't need to be repeated. Including, but not limited to, the stickie threads in this forum.
I'd also ask what the fish was fed prior to getting to you.
When small, the TSN I had would usually prefer fish, cut or whole, to pellets. Usually, no healthy and happy and well acclimated fish can refuse bloodworms or earth worms.
Bullying, bright light, no cover, inadequate aeration, wrong or unstable temperature or pH, wrong water hardness or salinity can all spoil an appetite of a fish too.