The curving courtship display of a female krib is one of the most beautiful displays in the realm of animal behavior. A pair of kribs with offspring is a formidable defensive team, often vanquishing much larger cichlids to the far end of the tank. Since the mid-60s people have recognized that not all kribs are the same. Red morphs have dark red opercula and a band of red from the edge of the mouth to the belly region. Yellow morphs have yellow opercula and yellow lips.
Male morphology is inherited, i.e., red morphs come from red morph parents.
But many did not. Some males became harem owners, courting and spawning with two or more females at a time. Satellite males lived in the territories of harem males, where they were tolerated, and helped defend the territory and the offspring in it. Sometimes these satellites mated with the females in the harem. Which behavior a male exhibited depended on two factors, his morph and his size.