I agree with all the above comments.
And simply for aethsetic reasons, both species being earth eating, substrate dwellers, wouldn't you think having the South American tank be populated with just the Geophagines as cichlid, but accompanied by geographically correct species such as S American tetras filling out the upper regions , much more appealing.
Instead of housing a geographically incorrect mishmash.
I believe the cichlids would too, instead housing them, as floor space and trophic competitors, rather a proper dither fish that adds the feeling of security cichlids often require.
And then maybe have a Central American tank with Thorichthys and equally geographically correct species such as Astyanax tetras, or live bearers,
My altifrons males easily hit 12" in time, and made a 150 gal tank seem tiny.

If you simply must use another cichlid as a tank mate, something with a totally different appearance and trophic style, but from the same geographical area often works much better in the long term, keeping aggression from destroying the hierarchy.
