There is no reason to discuss "Is it ok to put Labidochromis caeruleus with other tropical fishes", because L. caeruleus is from Malawi lake and water values are much more different than South America.
So, never mix Malawi with Tanganyika or Malawi/Tanganyika with tropical fishes. They do not belong to together. In both lakes water is basic for example, Tanganyika real basic.