Due to the high aggression from the dominant sev in the 90g, I decided to move him over to the 300 with the big Oscar. No issues whatsoever, the Oscar doesnt even pay attention to this fish at all. I was thinking the size difference would be an issue and its not. I know if I add the other two this (believed male) sev will start the whole process of dominance again since he will try to pair up with the female and likely make life miserable for the other male. Just not sure if the 8ft tank will make a difference in that regard or not.
Will say that I love the little splash of color that this solo red spot sev adds. Cant wait to get the clown loaches and barbs in the tank!