I have my bkg in a planted tank, I was forced to put in the three baby guppys that I found when I broke down my 25g. They've been there for weeks with 5 ottos too. I keep my bkg well fed and he doesn't bother chasing fish. I had a hard time to get him to eat raw shrimp bits. I think he recognizes the brine shrimp bits and bloodworm bits as his regular food source and hasn't developed a taste for live fish, or he's too lazy, relying on the easy food source that I provide.
I'm keeping watch on this, and if there is a problem he has a home waiting in someone else's tank. But I like him sooooooooooooo much!