According to those who have spent time studying/collecting certain Geophagus species in the wild, not all shoal, or even swim in pairs outside of spawning, so a lot depends on the species.
The bigger problem I see with this scenario is that G. steindachneri males, once sexually mature can become pretty relentless with chasing females. Forcing a "pair" together in a glass box is not going to be much of a life for a single female. She might be displaying dominance at the moment, but trust me that will change once your little male gains some size, and settles in to his new environment.
The bigger problem I see with this scenario is that G. steindachneri males, once sexually mature can become pretty relentless with chasing females. Forcing a "pair" together in a glass box is not going to be much of a life for a single female. She might be displaying dominance at the moment, but trust me that will change once your little male gains some size, and settles in to his new environment.