I've had RB's in with an Exodon for over a month now and they have not even touched him. I had some small tetras with them when I first got the RB's and they were gone the first night. But the bucktooth just seems to fit in with them, he is just as agressive towards the food as the RB's and will often fight them for food. I do keep mine well fed (3 times a day) so that could be the key to keeping them together.