What are you talking about? All my fish come from the same planet...that's the biotope I'm going for...
The biotope thing is a bit overdone, IMHO. As long as all the species do well in the same temperatures and water chemistry, I don't really care whether they come from the same creek or from different continents. We hear how this species and that species will do well because they both come from the same river, without considering that one might be found many miles from the other, in different depths, water flow rates, etc. I even see folks posting how different species from the same water will be temperamentally better suited to live together than those from far-flung habitats. Huh? Zebras and lions are found in exactly the same habitats, living side by side...but that doesn't mean they can be kept together. But zebras can be kept with other grassland-dwelling ungulates from Asia with similar habitat requirements because they will not interact in any way, good or bad.
I also see many comments made that a SA cichlid might have different disease resistances and weaknesses when exposed to an Asian fish with completely different parasites and pathogens. Makes sense, but...both of those fish have, by the time they land in your tank, likely been in a dozen different tanks and exposed to many dozens of different species from all over the world. Tanks are rarely emptied, disinfected and refilled when new fish come in; back when I worked in a pet store, the tanks were all on a single central filtration system, so basically everything was exposed to everything else. By the time you buy one of those fish...the "disease" ship has sailed. Quarantine is your friend, not some esoteric concern about biotope-correctness.
At the lake on which our cottage was built, we would catch Largemouth Bass in shallow sunlit lily-pad beds, and then motor or paddle a couple hundred yards and pull up Whitefish and Lake Trout from the dimly illuminated bottom in 90 feet of water. But I'd wager that an aquarist in Asia might put those fish together and call it a biotope pairing.
Addressing water temperatures and other parameters is much more important than worrying about being biotope correct, which is IMHO a feel-good aesthetic consideration; harmless but meaningless.
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