Dr. Erik Johnson is a world renowned veterinarian with a clinical specialty in fish medicine, and speaks and conducts seminars throughout the USA. He is the author of Koi Health & Disease, and Fancy Goldfish - A complete Guide to Care and Collecting.
Here's what he has to say on the subject of goldfish, and temperature......
"The temperature at which we should house our goldfish collections is the subject of debate. While it's true that goldfish of most varieties are extremely adaptable to a wide range of temperatures, there is considerable evidence that goldfish do best in water in the mid to high seventies.
Different varieties of goldfish also demonstrate different degrees of adaptability to temperature. The hardiest varieties, including Comets, Shubunkins, and Wakins, will survive winter in North America unless the pond freezes solid. The more highly selected varieties such as Orandas, Ryukins, and Ranchus may survive a temperate winter in North America when left outside, but in my experience they do this with less and less success as they mature.
Goldfish will flourish in water occasionally as warm as 102 degrees if it is properly aerated. I have customarily kept goldfish of all varieties in water as warm as 90F during the summer, and I maintain that warmer water is actually better for goldfish. My fish have shown superior growth and appetite, and the biological filter has performed best at temperatures in the mid to high seventies.
My point is not that the majority of your fancy goldfish will fall ill or die if left outdoors, but that there will be a higher incident of illness among these fish than if they were maintained at balmy temperatures year round.
Hobbyists who keep their fish outdoors with water temperatures near the freezing point may contest this, but, based on my clinical experience, I disagree."
Here's what he has to say on the subject of goldfish, and temperature......
"The temperature at which we should house our goldfish collections is the subject of debate. While it's true that goldfish of most varieties are extremely adaptable to a wide range of temperatures, there is considerable evidence that goldfish do best in water in the mid to high seventies.
Different varieties of goldfish also demonstrate different degrees of adaptability to temperature. The hardiest varieties, including Comets, Shubunkins, and Wakins, will survive winter in North America unless the pond freezes solid. The more highly selected varieties such as Orandas, Ryukins, and Ranchus may survive a temperate winter in North America when left outside, but in my experience they do this with less and less success as they mature.
Goldfish will flourish in water occasionally as warm as 102 degrees if it is properly aerated. I have customarily kept goldfish of all varieties in water as warm as 90F during the summer, and I maintain that warmer water is actually better for goldfish. My fish have shown superior growth and appetite, and the biological filter has performed best at temperatures in the mid to high seventies.
My point is not that the majority of your fancy goldfish will fall ill or die if left outdoors, but that there will be a higher incident of illness among these fish than if they were maintained at balmy temperatures year round.
Hobbyists who keep their fish outdoors with water temperatures near the freezing point may contest this, but, based on my clinical experience, I disagree."
