All the evidence would suggest that evolution has certainly done the job in that sense.
The fact remains the sort of fish I'm discussing have been successfully kept, maintained long term and bred all over the world for decade after decade after decade.
And yet categorically they are successfully kept all over the world under a variety of parameters.
There is no such evidence.
Your definition of "successfully kept" varies from that of many of us who agree with Nathan Hill in the blue citation in my signature block. And to Paul Loiselle's statement in green. There is scientific evidence--and it is irrefutable--that fish kept in parameters close to that for which they did evolve over thousands of years will have healthier and normal lifespans for the species. When the aquarist acquires the fish, the aquarist takes on the responsibility of providing the best reasonable care for that fish. That requires listening to and learning from the ichthyologists and biologists who have the knowledge. No one should be in this hobby if they are not willing to understand and provide for the fish's inherent needs; these have arisen throough evolution, and they are programmed into the species' DNA.
There is no evidence of evolution changing the inherent physiological needs of a particular species just because it is raised/bred in tanks for whatever number of years. In actuality, it is evidence that the particular species has an incredible will to survive in the presence of what is an inhospitable environment. Some species can adapt to some degree, and the reason they can becomes evident when one understands the physiology of that species. When this allowance is not present in the particular species, the fish can exist for a time, but it does not thrive for its normal average lifespan. It is fraught with health problems with which it would not otherwise have to contend.
Water hardness affects freshwater fishes in terms of osmoregulation. Water hardness also affects the regulation of blood calcium levels. Within any particular environment, fish have tuned their physiological functions to cope effeciently with a fairly narrow range of water hardness levels and therefore osmotic pressure. Altering the hardness values outside this range or disrupting the major ion composition of water hardness will lead to extreme osmotic stress and other physiological malfunctions. Different fish species have a varying resistance to changes in water hardness, depending upon their ability to alter their osmoregulatory process to changes in osmotic demand. Most fish can be acclimated slowly to abnormal water hardness. In general, however, they will be under unnatural stress and will not achieve optimum performance in growth, breeding or disease resistance. It is clear that it pays to provide your fish with water of the same hardness as they have evolved to deal with in their natural environment. [This paragraph cited verbatim from
The Manual of Fish Health authored by Dr. Chris Andrews, Dr. Neville Carrington, Adrian Excell, and Dr. Peter Burgess.]
This is a scientific hobby. We are keeping wild creatures that have evolved to their present state, and are continuing to evolve through natural selection. Every process within the confines of an aquarium is governed by the natural laws of biology and chemistry. There are trained scientists in this hobby, and they know better than any of us. When dealing with cancer I took the advice of the doctors and specialists. I did not listen to the "advice" of the nice lady who reads tea leaves at the county fair. They are worlds apart.