Regarding nutrition/diet, there are three main types of cichlids:

  • Carnivore: fish or flesh
  • Herbivore: plant and algae
    • Limnivore: periphyton growing on stones etc
  • Omnivore: not specialized

Carnivore cichlids have a shorter, but "rougher" gastrointestinal tract, while digestion of herbivore nutrition is "harder" and requires a longer, more fine-grained gastrointestinal tract. 

Feeding herbivore cichlids with a carnivore diet can seriously harm them.  E.g. Tropheus species from Lake Tanganyika can die if you feed them with red mosquito larva (bloodworms) due to small hooks that get stuck in their guts. A wrong diet will lead to the common "bloat" disease.

Vice versa, feeding a carnivore cichlids with herbivore food only will result in serious deficiencies over time as well, because a carnivores cichlid's gastrointenstinal tract isn't able to digest herbivore food.  The common "hole in the head" disease is a sign of deficiencies and thus a result of inappropriate diet.

Therefore, I strongly recommend not to keep both Carnivore and Herbivore cichlids in a single tank.  You cannot find an optimal diet for all your cichlids, and over time they will suffer from diseases and might die.