There are several species that could be confused with a johanni, but it's a pretty common fish, so I'd suspect that's what you have. It'll color up with maturity.
I couldn't disagree more with the suggestion that african cichlids are "very sensitive to ammonia and nitrites". Mbuna are about the toughest fish in the world. The downside with cycling is, that with an elevated pH like they prefer, more ammonia is in the "harmful" form. Do regular water changes, and use some filter media or substrate from an established tank, and that will speed things up considerably. Just test the nitrogen levels often and water change as needed.
They should eat just about anything. Stomach contents of wild specimens indicate a diet of most plant matter, so Formula 2 or a similar frozen diet is ideal. But flake or pelleted foods are usually taken readily.
Somebody needed to!