This is actually something I was thinking about awhile ago. At what size difference would a fish decide trying to eat much smaller fish wasn't worth the effort. I was going to grow the odoe, then have a massive school of small tetra.
I put the tetras in when he is in adult size. There's several factors that make it work. First, size difference. The tetras should be small that his effort to catch him outweighs the reward. 2nd, make it hard for him to catch them. Put plants, woods, even before you put the tetras in. 3rd, which I think is very crucial is, start the odoe early with non living food. This will prevent him from thinking of the fish as food (he will still but the other factors will help). 4th, feed him in one side of the tank and put the fish on the opposite side when introducing. Fish will know where food is dropped and will wait for it. I feed him on the left side, so when I introduced the tetras, they came in through the right side (important not to make a splash as this triggers hunter instinct).
