Not what I wanted to hear, any idea what I can have in my 5 footer along with a single Vieja Synspillum then ?
I would grow out a few juvie Vieja, and allow them to choose another of the same species tank mate.
As far as other species of fish, my choice would not be other cichlids, but geographically correct dithers, like Astayanax (or other) tetras, or large sail fin mollies.
Thaese non-cichlids would act as dithers to help the Vieja feel comfortable (as they do in nature).
V melanurus (formerly synspillum) are not really predatory (piscivores), so if tank mates were not an easy to catch protein snack (not small enough to easily eat) they could work,
Non-cichlid dithers are even a possibility with argentea (mas o menos) because they are not often considered competitors the way other cichlids are.
Although there are no Vieja in the video below, it was taken in the same area of southern Mexico V melanura live, and represent the common dither fish cichlids share habitat with there. And that in a large area you may only find 1 or 2 cichlid species (not varied communities like like in Africa or S America).
027 zps4b102ffd
Azul imovie edit
In nature you "hardly" ever find 2 of the same (or similar genera) genus together because of the competition for similar resources.
But aquarists often tend toward keeping similar shaped, or looking fish together because of human visual preferences, and when the cichlids are juvies this practice works for a while, (they see safety in numbers) but at maturity its like a switch is flipped and the smaller the tank, the worse the reaction.
In your size tank, if you want more than one species of cichlid, choosing very different looking species often works.
Since you seem to like the Vieja look, something like Oscura heterocpilla, combined with a more elongate, cichlid like a Rheoheros lentaginosus below
or different shaped mouth type like those of the genus Thorichthys might work.
