The reason they usually don’t live long is that people think they can be kept in small bowls full of putrid water, or they put them in with tropical fish. Also, people buy 25 cent “feeder” goldfish which are unhealthy, overcrowded, starved, and sold with the expectation that they’ll only live long enough to get to whatever is going to be eating them (big fish, snakes, whatever).

A goldfish needs a minimum 10 gallon tank with good filtration, and they need to be kept cool — they’re coldwater fish, and can’t handle warm temperatures any more than tropical fish can handle cold water. Larger tanks will be needed as the fish grow. And no, they won’t stay small if you keep them in a small tank, except to the extent that their growth is stunted because they’re sick or dying.

A properly cared for goldfish will grow to the size of your hand (or bigger!) and live for 15-20 years on average, with the record being over twice that.

This stuff is cool despite of its low lifespan…