How Many Gallons Of Water Do Goldfish Need. Ask any fish owner and they’ll. If you have a larger tank, you may want to increase the size of the tank.

In aquariums, adult common goldfish, comets and shubunkins should have at least 20 gallons of water per fish, while adult fancy goldfish should have at least 10 gallons per adult fish. How many gallons do goldfish need? Your typical comet goldfish will need at least 30 gallons of water each to stay healthy long term.