Gold fish and Other Fish
(Wausau Wisconsin USA)
Do I need to have a heater in my fish tank?
I have gold fish and some other fish which the store said you can mix.
Goldfish don't normally need a heater, especially if their tank is indoors.
The requirement for a heater will depend on the temperature requirements for the other tank inhabitants.
Goldfish can tolerate a wide temperature range, around the average maximum highs and lows for Wausau, but the other fish may not.
Do some research on the other fish and if they don't have the same tolerance range, install a heater. Keep it at the lowest setting the other fish will accept.
Some form of water circulation will be required such as a filter or aerator to keep the water temperature even throughout the tank.
Regarding the other fish, if your goldfish are one of the twin tailed or telescopic eyed varieties, they may have difficulty competing for food.
Also, watch for fin nipping if your goldfish are long finned.