Nelson,
Generally, a change in the decor of the tank usually chills out males and colonies for some time. I have to confess I am not sure what a dogtooth is, as I'm not that great with common names. A Scientific name might help a bit.
I think all other responses first will probably ask, what size tank is this and is that all that is in the tank? What species are we talking about? All four same species? Sex ratio?
I have kept Africans with South American Arowana, they actually mixed quite well as I kept the South Americans on a proper diet of surface food only. I did for a year manage to keep a Jardini with them, but after a year of maturity, fish started disappearing so I had to sell him.
If it's just a matter of an aggressive African, I can only suggest changing up the decor, but again I don't know much about what a dogtooth is really. I am assuming you've got quite a massive tank, something in the order of a 250 gallon plus? I'm also guessing a dogtooth is more like a Hap or Peacock since Mbuna really wouldn't dwell up in the same area an Arowana would.