I think he meant more then one Red Wolf would kill each other.
I have mine all in a 55 and I plan on keeping there for a very long time. They have been fine for a month so far. The Red Wolf is 5" and the Bichirs were 3.5" when I introduced them so he could have easily eaten them. I was scared he was going to when I introduced them because he rushed them like they were food but he ended up stopping and just staring at them.
Every once in a while I'll see him chase them off but most of the time they are fine, they even chill in his cave sometimes.