The ever-popular goldfish in a bowl has been part of children’s ‘first pet-experience’ for years. I had one. You probably had one. Your friends had one. My friends had one. Until it died of course, which usually happened within a month or two. Sad, but not unexpected – after all, goldfish have a life expectancy of about a year, right? Unfortunately, it’s not that simple. Goldfish can live for up to 20 years, but often die prematurely because their owners keep them in bowls or very small fish tanks.
Keep reading for more information about what a proper goldfish aquarium looks like and why bowls are bad.
Due to their active swimming behaviour, two common (single tailed) goldfish need a tank that’s at least about 6.5 feet! Commons are actually best kept in ponds because of this. Fancy (double tailed) goldfish are more suitable for life in aquariums, but at least 20 gallons per fish is still recommended. But why do they need that much space? Are they secretly throwing huge parties at night, while you’re asleep?
What a lot of people don’t realize when they win one of those tiny little common goldfish at the fair, is that even though it’s barely 3 inch now it actually has the potential to grow to up to 15 inch (40cm) or more! That’s the size of my underarm, and even though I haven’t checked, I’m pretty sure my underarm doesn’t fit in a goldfish bowl. But a goldfish can adapt its growth to the size of the bowl or tank it’s kept in, right? Well… kind of. But not really.
What actually happens in a bowl or small tank is that the exterior of the fish stops growing, causing it to remain the same size. However, the organs continue expanding in size, and so do the spine, eyes and fins. Eventually, after the organs have been squished together and the spine is bent into an S-shape, the fish will die.
Another good reason to avoid keeping your goldfish in an unfiltered bowl or vase is the amount of waste they produce because of their mostly vegetarian diet, and the problems this can cause. A lot of “bowl-goldfish” die because of ammonia poisoning – their gills, fins and skin get burned by the ammonia they excrete, resulting in black burned areas and eventually death.
This is why goldfish should always be introduced into a fully cycled tank, and why double filtration is always a good idea – for a 50 gallon aquarium, that means either two filters meant for a 50 gallon, or one meant for a 100 gallon. External canister filters are best, as they have room for biological filter material. Insufficient filtration can cause ammonia and nitrite spikes.
Goldfish need a lot of oxygen. Because of the lack of surface area the water in a bowl or vase can easily become de-oxygenated, causing the fish in it to slowly drown and gasp for air at the surface. This is often mistaken for begging for food or giving kisses by inexperienced owners. An air stone is not always the solution – it just doesn’t create enough surface movement for new oxygen to dissolve into the water.
To provide your goldies with enough oxygen, get a tank that’s large enough – preferably one that’s rectangular, so there’s a lot of surface area. If they still gulp air, getting a pump, large air stone or a filter that creates a lot of surface movement might be helpful. If the problem still isn’t fixed, there might be a problem with the food – fish flakes are not proper goldfish food because they’re not nutritious and can cause swim bladder problems. A good quality pellet food like New Era may help.
Water values and temperature
The smaller the aquarium, the bigger the effects of small changes in water quality and temperature are, which is why large tanks are much easier to keep stable. A very small amount of nitrite may not be fatal in a 40 gallon aquarium, but the same amount of nitrite can easily kill a fish in a bowl or 5 gallon tank because there is less water to dilute it. Getting a filter for the bowl won’t be a solution either, as filters just can’t cycle in tanks this small and won’t be able to handle the amount of waste a goldfish produces.
Temperature fluctuations are also much more extreme in small amounts of water, because there is no buffer that slows the changes down. This can be very bad for your goldfish – the stress affects its immune system, making it more susceptible to diseases and parasites.
Keeping goldfish in bowls, vases or small tanks drastically reduces their life expectancy and quality. It causes them to get deformities, burns, stress-related diseases and in some cases they even choke to death. In some countries, goldfish bowls are actually banned – and for a good reason.
Show some respect, even if the animal is not cute and cuddly. Goldfish are not throwaway pets. They do not have 3 second memories. They are not decorations. They are not toys. Just like any other pet, they need space, a clean environment and company. If you do not have the money to provide them with this, do not buy them.
For more information about keeping fancy (double tailed) goldfish, have a look at the fancy goldfish caresheet. For more information about keeping common (single tailed) goldfish, have a look at the common goldfish caresheet.
If you have questions about your own goldfish, want to share your experiences or have something to add to this article, leave a comment below. Happy fishkeeping!