I had Oscars years ago. 55 gallon tank had two Tigers and one that was the color of a brand new copper penny. They were easy to train. I used to buy #3 trout pellets fot r treats. I'd soak them in water until they were soft, pick them up one at a time, and hold them half way in the water. The fish would swim up and take them from my fingers. In a couple of weeks, I had them where they'd clear six inches of air and jump to get 'em. Funny as h ell when one of my friends would ask to feed 'em and hold the pellet a few inches from the surface. The look on their faces when they'd get fish bit was golden.