Most people assume goldfish are small, easy to care for fish that don’t live long or need big tanks, however this is completely wrong.
1 Goldfish can grow over a foot long
Goldfish can grow very big and very quickly with the right care, though if kept in unfiltered small tanks they will be stunted due to bad water quality (which is very harmful to them and should never be done or encouraged)
The largest recorded goldfish measured 47cm long. They can become enormous.
The large fish you see here is 16 months old and about 20cm, the little ones are about 4 months old and 6–8cm, and they will catch up.
2 Goldfish need big tanks, bowls are NOT suitable
You may commonly see goldfish kept in bowls but they are not appropriate environments for any fish, least of all goldfish.
‘starter kits’ are commonly sold as perfect environments for goldfish when within a couple of years they should be bigger thank the bowl. In bowls and small tanks water quality cannot be maintained and kept safe, resulting in ammonia levels building up and harming the goldfish. The waste they produce is toxic and if water cannot be kept at safe levels it can seruouslt harm or kill them.
Here’s a good size comparison showing how adult goldfish literally cannot even fit in these starter kits.
A good way to determine appropriate tank sizes is to keep the fish in a tank 6x its adult length, so goldfish, all of which can reach around 1 foot long, require a tank of at least 6 feet long. Not a 6 inch bowl.
3. Goldfish can live for decades
Often people assume goldfish are a very short lived pet but that is also very untrue. They only live short lives due to bad care (sometimes genetic problems can affect their lifespan too)
Fancy goldfish should live around 10 years, often more depending on the type.
Single tailed goldfish should live over 20 years, the oldest recorded goldfish lived to over 40 years old.