Iridescent shark not eating? help?

i got my id shark about 3 or 4 days ago and i havnt seen him eat once yet. he lies on the ground around a skull swims some what at night up and down against the glass in one spot near his skull that he lays in and near. i have one other fish which is a pineapple swordtail which doesnt even go near the id shark and some ghost shrimp that also leave him alone. the id shark is about 5 inches maybe a little smaller. what is wrong with him? is it stress? being lonely? i dont think its disease because his colors are fine but he does have a white almost hole looking thing on his nose but i think thats from him freaking out and ramming the glass. help on what can be wrong? also i feed my fish freeze dried blood worms tropical fish flakes and shrimp pellets. do i need a specific food for the id shark because i know he is really in the catfish family