People are usually surprised at both the normal life expectancy and size that goldfish reach.Goldfish Size and Life Expectancy
If kept in a suitable environment, single tail goldfish normally grow to 10 inches (25cm) and can sometimes reach 12 inches (30cm). Fancy goldfish normally grow to 8 inches (20cm).
The normal life expectancy of a single tail goldfish is about 20 years. Fancy goldfish have a life expectancy of about 12 years.
The following diagram illustrates this:
Why are these sizes and life expectancies so surprising to most people?
This is due to the poor conditions that many goldfish have been traditionally kept in. Goldfish kept in bowls or tanks that are too small will suffer from poisoning due to poor water quality and internal organ compaction due to a lack of space. These problems both shorten a goldfish's life and stunt its growth leading the misconception that goldfish are small, short lived animals.Tank Recommendations
This website recommends the following minimum tank sizes for keeping goldfish:
Common Goldfish: 40 gallons (48 US gallons, 180 litres) for the first fish with an extra 12 gallons (14 US gallons, 55 litres) for each extra fish. The tank needs to have a minimum length of 4 feet (120cm) to allow swimming room. Single tail goldfish are more suited to a pond when they are near full size to give them swimming room.
Fancy Goldfish:30 gallons (36 US gallons, 140 litres) for the first fish with an extra 10 gallons (12 US gallons, 45 litres) for each extra fish. The tank needs to have a minimum length of 3 feet to allow swimming room. In addition, an external filter is highly recommended.Help is at hand
Goldfish do make rewarding pets, they love eating and will feed from your hand. They are much more intelligent than most people think and have an appealing clumsiness about them - much like a Labrador! If you find yourself with a goldfish in an unsuitable home there a few options open to you:
If you've just bought the fish or tank take them back to the shop and ask for a refund. Tanks too small for goldfish are not fit for purpose so you are legally entitled to a refund.
Re-home the fish - single tail goldfish are more suited to a pond but don't transfer them in the winter. For fancy goldfish you might find someone to adopt them. It's illegal to release goldfish into the wild.
Get a bigger tank. Your local tip, eBay and Freecycle often have free or cheap tanks. Check they are water tight outside first!If you find yourself in this position you are not the first and not alone. Many members of this site have been through this so post your questions in the forum and someone will be able to help.Further reading
Some links to further helpful articles:Keeping Goldfish the Right WayFishkeeping MythsPoster Download
If you would like to take a copy of the size chart to your local shop for them to use you can download a PDF copy of it here - Poster Download