To me nanoluteus small size, restricts there tank mates to something like other geographically correct live bearers, or other small non-cichlids. When I tried to keep mine with other cichlids, (although they held their own) the nanoluteus seemed to not show the brilliant colors they'd show if kept with less stress causing tank mates.
Poecilia gillii, or the genus Phallichthys are live bearers that might be found in the same Central American waters, and would inhabit the surface areas of the tank providing the appropriate dither effects that cichlids appreciate, and action in different areas of the tank.
Or Olimina (flame rivulus) killifish are also from the same waters in Panama and Costa Rica where nanoluteus are native, but many other killifish are beautiful and different enough to not seem to be competitors, and stress out the cichlids.