Anything that stays under 7-8".
Convicts, or any fish from that family. Also, you need to specify the type of fish. IE: African, SA, CA, mollies, tetras, dwarf cichlids.........
It not just overall size of the fish that you have to worry about, its the aggression from the male towards the female in the Cichlids. If the male feels like he doesnt have space, he will relentlessly seek out that female.
If you like SA and CA Cichlids, then Google small C & SA cichlids and check out the images, see one you like and ask about them.