How long has the Oscar been living with the Tiger Barbs!? He must be a vegetarian. Firemouths are a great Oscar tankmate. They can stand up for themselves if they need to.
Please realize that I am being completely encouraging and constructive when I say that that O needs a more balanced diet. He should have much more red on him than he does there.
Feed him some food with beta carotene or if you make your own food add minced carrots to the gelatin pellet mix. He'll look much happier and healthier and become a great show piece.
The tiger barbs have been in there a long time. Tiny the Oscar ate a couple but normally cannt catch them. The pics kind of washed out red on both Oscar and firemouths . I will get some new pics and some of the Dempsey and Texas which share the tank.