Following up on the previous post, you can't make general assumptions about cichlids based on reputation or characteristics. Why? Cichlids have their own personalities. Yes, some are genetically predisposed to aggression. However, there are exceptions.
To carry this farther, don't assume that larger cichlids have an automatic advantage over smaller species. Yes, if the size differential is significant and the larger cichlid can fit the smaller cichlid in its mouth, then it matters. Otherwise, many smaller species can easily hold their own against much larger tank mates.
Have you ever witnessed a crow harassed by a mocking bird? Many similar examples exist in the world of cichlids. Try to convince a fry guarding female Telmatochromis sp. "temporalis shell" to back down from any other cichlid of any size. Same for a male N. ocellatus.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub