How Much Tank Space Do Goldfish Need?
Believe it or not goldfish may be one of the most abused pets. Often kept in tanks, bowls, and aquariums that are too small for them, many are stunted in size as a result. Perhaps it is because goldfish are cheap and easy to come by, that people fail to consider their needs to be important.
Goldfish were once thought to be stupid, with only a 10 second memory. This has been disproved as goldfish have been taught to swim a maze, and push balls through hoops. In fact their memory has been shown to be around three or four months. Yet many are kept in tiny bowls with nothing more than a plastic plant.
Goldfish have a lifespan over 12 years (one common goldfish lived to be over 40 years) and some varieties can grow to 16 inches (40cm) yet in many homes they live only a few short years and are often very small for their age. Why is this?
At one time people were told that it was okay to keep their pet goldfish in a small tank, they were told it would adapt to the small bowl and only grow to a smaller size. Indeed while this is true, it is not because of some great fish miracle, it is because in small bowls the water becomes extremely dirty, even within a few hours, poisoning the fish, and stunting its growth.
In many cases their growth is further stunted since many of the goldfish kept in bowls do not have aerators, the lack of oxygen in the water is also a contributing factor to stunting growth in these fish.
A general rule of thumb for keeping any kind of fish is that the tank should be at least 1 gallon of water per 1 inch of fish. As such a fish that is 4 inches (10 cm) long would require a 4 gallon tank. Two fish of similar size would require an 8 gallon tank. But wait, you must also consider the size the fish is expected to grow to. Comets, shubunkins, and common goldfish tend to grow larger than fancy goldfish, and may do better in ponds rather than in small aquariums or tanks.
If your goldfish are expected to grow to 10 inches, and you have two, you would want to keep them in a 20 gallon tank, not a traditional “goldfish bowl”. It should even be noted here that goldfish bowls have been banned in Rome due to being considered as cruel.