Betta fish life span in a bowl

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.