actually, most goldfish are classed as sub tropical...
yes they are carp related and they get HUGE and old, but they fare in slightly warmer water just as well as cooler water.
Yes his waste products are a little much to deal with so we do major water changes all the time, really don't mind it. As for my goldfish he loves being in this tank, He is a big baby and loves affection. You would think that as big as he is that he would be kind of bossy but that isn't the case at all everyone just pushes him around and he allows them to chase him for a few seconds. He is great to just sit back and watch.