I have tried multiple times to reintroduce and see how it does but it has not done well with the other wild Oscar. It seems to only know one thing and that is to nip and bite. There is a subtle show of dominace from the red toward Oscar #2 but it is within normal safe pecking order stuff. oscar #1 just goes at the other wild like its just trying to bully it to death. At this point they are pretty much the same size with #2 being slightly bigger even. But its all about attitude and #1 has it and lots of it.