Originally, many cichlid species were grouped in the same genus, "Haplochromis." But taxonomists broke the genus up and moved most species to other genres, giving them new Latin names. But the name Haplochromis, hap for short, wouldn't go away. Now several different groups of chiclids are known as haps.
Technically, the only true haps are those in the genus Haplochromis. These fish are found only in Lake Victoria in Africa's Rift Valley. However, a number of other cichlids from nearby Lake Malawi were included in the genus until it was split up. In this case, the common name was based on the scientific name and then the scientific name got changed. However, there is still a large, recognized group, "the hap group," for all the fish in these related genres. Additionally, some people call any Rift Valley cichlid that is not a mbuna (rock-dwelling cichlid) a hap.
There are three major groups of haps. The first is the utaka. Unlike many cichlids, which tend to live near rocks, utaka haps school in the open water, albeit not too far from the shore. Large, mostly female groups do well in large aquariums. They get along with other fish, even the mild African cichlids that will not bully them. They eat zooplankton in the wild but will accept prepared food in captivity (preferably with the occasional live treat).
Predatory haps are large; they eat other cichlids. Like the utaka, they are more transient than most cichlids, which usually stake out territories among the rocks. Several females can share the largest of aquariums. However, keeping more than one male will result in constant, brutal fighting. It is not recommended to keep more than one male predatory hap in a tank. Sometimes, though, they can get along with other cichlids that are not aggressive and are too large to eat.
The miscellaneous category of haps includes any hap not considered a utaka or a predatory hap. They include a wide variety of feeding behaviors ranging from vegetarian to fish eaters (but in this case, the fish eaters are smaller and much less aggressive than the predatory haps). Like other haps, having more than one male of a species per tank is a bad idea. Even then, they do require very large aquariums with lots of rockwork.