@Salty&Onion
Its the longterm affect that you need to worry about. Fish can handle *temporary* high or low temps out of their range. But they are cold blooded and have evolved in certain habitats. When kept outside of their natural range, you put stress on their bodies.
1. It messes up their metabolism, as mentioned. Speeds it up in hot temperatures so their bodies have to work overtime to keep up or slows it down in too low of temperatures and backs up their systems.
2. It is a constant stress on their immune system. This may not kill them outright, but it makes them more likely to become sick where an unstressed fish would remain healthy. If disease or parasites is introduced, they would be the first affected. And, you should know some pathogens are naturally present in our water, waiting to affect compromised fish. This stress wears down on their lifespan as well in the long term and they will not live out to their full potential.
3. You cannot change evolution easy. Just because it's born in captivity in those temperatures and kept that way for a couple decades, it does not change millions of years of evolution.
As fishkeepers, we take these creatures out of their wild habitats and make them live and breed in little glass boxes. It is our responsibility to make sure theyre given the conditions they were evolved to live in, a suitable thriving habitat, and give them a life worth actually living. Many millions of fish go to homes who don't know any better. Those of us who choose to actually research the fish in our care and are in this hobby have a responsibility to the fish in our care.
