I have a small, round, glass fishbowl on my desk. It’s about 6 inches in diameter… about twice as large as a typical Betta bowl… and I’m thinking about getting a small aquatic “pet” for the office.
I could do the obvious thing and get a Betta, but I was thinking that a pair of Guppies might be better (since they wouldn’t be alone all the time). And I think Guppies are hardier than Bettas and it can get cool around here over the weekend (I live in Norhtern California so it doesn’t get that cold or hot on weekends). Any besides, Bettas prefer live food and Guppies like flake food.
So what are good fish or other aquatic candidates for an unfiltered smallish fishbowl?
A six inch bowl cannot provide enough water with enough oxygen to support the metabolic needs of even a small fish. The small amount of water would get dirty very fast, too.
Bettas can be kept in tiny containers (although it’s not nice to do so) because they have a special organ, called the labyrinth, that allows them to breath oxygen from the air.
The rule of thumb, when I was growing up and keeping fish, is that you need a gallon of water per inch of fish. So one little guppy needs one gallon, two little guppies need two gallons, and then they do their fishy thing and have six babies, the family will need eight gallons (if they don’t eat the fry first). On top of this, you really are supposed to have a bubbler and a filtration system. The bubbler helps to aerate the water (if you don’t have one of those, then you need a very large surface area to let gases diffuse) and the filtration system helps to keep particulate matter and/or (depending on the kind of filter) ammonia levels sub-lethal.
You could get a betta for your tiny bowl, but that’s about all that would survive long-term.