Originally Posted by aura09
gold fish ARE coldwatere fish and exposed to high temps although they will be able to survive in warmer water is bad for them over the long run messes up with there insides so def keep them in a goldfish only tank with no heater :)
An unheated tank is not the same thing as a coldwater tank. In many cases, unheated = subtropical. Coldwater generally means 70 degrees or less. I think most people don't keep their houses in the 60's, so how would you expect someone to attain these coldwater temps? Maybe there's someone here that does, but I've asked on other forums how many goldfish keepers have chillers on their tanks. None of them do. None.
Moreover, there seems to be a great debate over whether the fancy goldfish like are "coldwater" fish as well. I have heard compelling arguments stating that the egg shaped goldfish do best in warmer water. Your claim that warm water "messes up with their insides" is rather vague. What exactly goes wrong? How is the water temp responsible? You can't just make claims without at least explaining why you think it's the case. The truth of the matter is that they are ALREADY prone to internal organ issues because of their physical deformity. I don't know how you can attribute something like water temperature as the cause when it's a pre-existing condition.
I'm not advocating goldfish as a tankmate for discus, but rather pointing out that this notion of what coldwater is is a little misplaced.