My choice for tank mates would be geographically correct Astyanax, or other Mexican tetras ( Those the argentea share habitat with).
One of the other ways I found, that seems to temper their tendency for hyper aggression, is to supply enough current along the length of the tank to simulate the riverine environment where they live, and those type tetras are also comfortable in that environment.




In nature argentea and the tetras, have devoloped reserves of energy to cope with that rheophyillic constant current, and share the same rocky habitat.
And beggars can't be choosers in this food desert, so being an omnivore and accepting whatever float by, would need be used.
And any excess energy not used in coping, seems to be often directed as aggression in large enough tanks.
These rocky habitats are home to lots of shrimp and snails, and the cichlids that live in them, take full advantage of what's available.


And that prominent argentea mouth, is perfectly adapted for pulling snails, and shrimp from the rubble, but also adapted for whatever falls in the stream from thick overhanging vegetation, even if there is little in the form of aquatic plants.


I suppose these tetras are not the most attractive, but in reality, if the argentea are a primary focus of the tank, would you want some flashy orange subjects to steal the cichlids thunder?
