A 75 with a group of nanolutea and dither fish would work well.
I have kept both species but I would never keep them together
If it were me, I wouldn't add any other cichlids at all, especially another Amatitlania such as sajica.
There are two major issues with adding another species of cichlids, and especially Amatitlania.
One is territoriality, the other is cross breeding and ending up with mutts.
Male sajica get about 5 Xs larger than nanolutea and are very territorial, an adult male could easily tear any nanolutea to shreds, and probably would, because a 75 is a rather small footprint for them as adults, my male sajica killed any other cichlid i tried to house with it in a similar size tank (including other male sajica).
A full grown nanolutea will get about the size of the female sajica in the pic below.
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My nanolutea did well in a heavily planted and rooted tank.
They share their natural habitat with live bearers, like the local Panamanian mollies, with tetras that would include Astyanax, Hyphobressobrycon, and Roeboides, and small gobies like Awaous, and these would all make interesting and diverse tank mates. The live bearers and tetras would tend inhabit the mid and upper regions of the tank, and nanoluteus the lower areas nearer the substrate.
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Awaous goby below
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and some Panamanian Roeboides tetras below
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