Can you mix freshwater coldwater fish and tropical fish in the same aquarium?
This depends entirely on what fish you are wanting. Usually it is a question of wanting to mix a goldfish with various tropicals. The myth here is that goldfish need to have coldwater. The truth is that they can survive in colder waters, not that they thrive in them. Most fancy goldfish actually prefer a temperature in the mid to upper 70s (F). Most tropicals prefer a temperature around 76-82 (F) depending upon the fish. If you choose the lower ranges with fancier goldfish you have an ideal temperature match. The other complaint is usually waste output. But that is needed to be dealt with with regular maintenance. A goldfish does not produce any more waste than any other fish of it’s build and it needs to be planned for when caring for it. This is no different than all fish care/preparation. I have regularly had at least one tank with a mix of two.
