Well,If larger water changes are started from the beginning, and regular, then this would be all the fishes know.
In aquariums where water changes have been infrequent ,then fishes will have adapted to whatever the condition's might be (or not),It's not like they have much of a choice .
They either adapt ,or become sickly over time, and or expire.
Is tempting to bring a tank ,or fishes around with largish water change for the benefit's that clean water can provide, but I try to do it in a gradual way, lest the sudden change create more stress to osmoregulatory system of the fishes I care for or adopt.
I find for my tank's,,that 50 % water change each week or two keeps fauna and flora in good shape.
Is also why I perform a normal 50 % water change a day before,or hour's before introducing new fishes, or fishes from quarantine.
In this way,they have approx. a week before I perform another water change to allow for longer period to adapt.
Opinion's vary,but is my thinking.