Yep, don't even try. They are both in a group called mbuna. Mbuna are insanely aggressive, and insanely active. This means that you should have at least 4 of one species (1 male/3 female), with demasoni being the exception. With demasoni, although they aren't as large, but they are more aggressive than many others. So basically, get a tank 4 feet, about 15 demasoni, 4 yellow labs, and it will be awsome.