A cichlids mouth really is a multi purpose tool designed for maximum survival. Cichlids actually have two sets of jaws. There is an inner jaw that is used to mash its food leaving the outer jaw free to evolve specialized teeth which allows them to gather all different types of food available.
Fine toothed rasps, designed to graze algae
Interlocking and spiked teeth for catching prey.
Chisel like teeth for algae grazing and small organisms
These teeth are also of the grazing type but unlike algae grazers these are designed to graze scales off other fish. While of predatory nature, the prey survives the attack to regrow its scales for another meal to be had.
The mouths of many cichlids also provide another function, that of spawning and rearing their fry. They lay their eggs on the ground or rock in a spawning ritual with the male. They collect the eggs off the ground or rock, some do so in mid water and the male fertilizes the egg whilst in the mothers mouth. The mother then carries the spawn in her mouth until fully developed at which point they are released.
Cichlids have a strong nurturing parental nature and will look after their spawn even after they are released from the safety of their mouth. When danger is looming she will gather the fry in her mouth and seek safety, to release her fry again when the danger has passed.
Cichlids also use their mouths for protecting territory from invading males. If two males mouths are of similar size then a competition will result over who is the dominant fish. They will lock jaws in combat, twisting and fighting until one of the males succumbs and a victor is presented. Quite often the mouth of the loser is damaged but they will survive, temporarily beaten until they challenge another. More often than not, a cichlid will not risk injury to itself if they are not well matched in size.