I have an aquarium housing moors and an oranda. What is a safe temperature range for these fish? There seems to be conflicting information on this online.

My aquarium is in a conservatory and in the middle of winter the water temperature can get as low as 8 °C (45 °F) and in the middle of summer (currently) it can get as high as 30 °C (86 °F).

Last winter I only had moors and noticed no ill effects of the lower temperature. Some online sources seem to suggest orandas are more sensitive to temperature than other types of fancy goldfish, is this correct? Next winter I will most likely heat the water, but to what temperature?

With the increased water temperature in summer the only difference in behaviour I have noticed is that the fish will occasionally go to the top of the tank to get air, presumably due to the hotter water having lower oxygen levels. The use of an air stone seems to stop this behaviour. Are there any other risks at this temperature?

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You're correct about the oxygen. Warmer water dispels oxygen faster than cooler water. Sometimes the water returning from the filters is enough to add enough oxygen for fish, but sometimes it does help to add an air stone. Like you've discovered.

I've heard of people keeping goldfish in the same temperature range as tropical fish, but in my opinion they really shouldn't be. Goldfish come from colder northern waters. By my standards their temperature range is just under what I put tropical fish at.

I put most tropical fish between 75 - 85° F (roughly 23 - 29.5° C), whereas I put both goldfish and koi at 65 - 72° F (roughly 18 - 22° C). Goldfish are generally quite hardy fish, which is why they're usually used as first fish for most people, so you can probably get away with different temperatures, but that's where I've kept mine.

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