It's wrong, different water conditions, dietary requirements
These arguments, come on....So what you are saying is you have individual tanks for fish from various parts of the world and do NOT just use tap, you condition the water of each individual tank to the specific "requirements" of that region? You also do NOT feed pellets or flake to said different fish, you individually source specific food for said specific fish? I really dislike when people use those as an argument for mixing fish. If you want to say a dovii will murder all other fish in the tank at some point so should be housed solo, okay I can get behind that, but water conditions and food...