For me its about maintaining a proper biotope, but.......
there are other reasons beyond geographic aesthetics that come into play.
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Above is the type water many S Americans live in, below the type water many Central Americans have evolved over millennia to live in.
Quite different
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There are also difference in aggression tolerance, current strength, and topography that come into play in keeping fish healthy.
The bacteria that live in a high pH may be quite different from those low pH water, and fish endemic to one type may have little to no natural resistance to bacteria in another type.
This may contribute to why there are so many posts of oscars and others in the disease section with hole in the head, while other fish in the tank are HLLE free.
I consider the differences in collection point charts above as significant as salt water to fresh.
So randomly combining a cichlid such as a severum that needs mineral free low pH (below 6) water with a Texas cichlid evolved to live in mineral rich, high water (8+), or rift lake cichlid from high pH (8+)rocky habitat, with a South American like a Geophagus that live in pH 6 or lower water that live over sand, in high current less than intelligent fish keeping.