Do goldfish need a heater

Best Answer - Chosen by VotersWarmer is better. Fish diseases thrive in cold water. Goldfish don't require warm water, but it is healthier for them. Goldfish are cold water fish because they can _tolerate_ cold water, but it isn't ideal for them.

I would keep it between 75 and 82 degrees. Goldfish can tolerate constant water temperatures up to 90 degrees. Higher than that is bad for them though.

Be aware that warm water holds less oxygen, so the higher the temperature, the more water volume you need to give them. The standard formula of 2 gallons per inch of fish (not including fins) is assuming coldish (60s or lower) water. If it is warmer than that you need to give the fish more space.