What size bowl or tank can you keep your betta fish in? Opinions vary widely, but anything between one and five gallons is probably okay for a single betta fish. Half-gallon bowls can be used, but you’ll need to change the water every 2-3 days. Ideally, the bowl or aquarium should be at least 2 gallons. With a 2 gallon tank, you’ll probably be able to keep your betta healthy with water changes every 7 to 9 days. One gallon bowls need to be cleaned every 5 days. This assumes, also, that you aren’t overfeeding the fish.
In a recent poll, International Betta Congress members voted on the size of the tank they use for spawning a pair of bettas. 26% of them use 5-gallon tanks or smaller. 61% use 10-gallon tanks, and 3% use 20-gallon tanks. If 87% of those respondents think a 10-gallon tank or smaller is okay for two betta fish, putting one betta in a 4-gallon bowl will probably be just fine.
It’s also wise to use the old aquarium to fish the golden rule of one inch of fish per gallon of aquarium volume. At 3 inches in length, that would mean the average male betta needs a 3-gallon tank.
Other sources on betta fish aquarium size have focused more on the length and height of the bowl rather than its volume. They recommend betta aquariums be no more than a foot deep, and should be at least 6 inches wide. The depth is important because in the wild bettas live in very shallow water – frequently 6 inches or less, often only 2-3 inches. The length of the tank is important so the fish can swim back and forth and get some exercise. Though 6 inches is the length quoted for the fish to get some exercise, realistically it seems a fish would need at least 12 inches length and width in a bowl (or a tank) to really get moving.
A “baby” 4-gallon biOrb aquarium kit is 13.5 inches in diameter. While this is considerably more expensive than just a basic glass tank, it is a complete system, and its nicer looking than a square tank would be. If you want to have a betta in your office, the biOrb is a good choice. It comes with a filter, a heater, and a light, so while its more expensive than a straight glass tank, after all the extras are added in, its about as much as a traditional tank.
Some commercially available data bowl containers are 1/2 gallon or even a quart. For those of us who forget, there are four quarts in a gallon. These containers are just barely adequate. If you really want your fish to live for more than a year, you need a larger bowl. A 2 1/2 gallon standard size tank is 12 inches long, 6 inches wide and 8 inches tall. This is a pretty good choice for a betta aquarium – though you’re going to need to fill it up to only 6 inches deep so the fish has a harder time jumping out. This will reduce the tank volume to about two gallons.
A five-gallon tank is ideal. At 16 inches long, 8 inches wide, and 10 inches tall, the fish will have plenty of room to move around. If you aren’t using a cover on the tank, keep the water level two inches below the rim as a jumping barrier.
Having a little extra room to allow you to keep a cleaner fish in the tank, too, which will, as the name goes, keep the tank cleaner. Chinese algae eaters, clown loaches, and other kinds of small catfish are good choices. You want something that will stay small and is non-aggressive. If the pet store doesn’t have anything like that, opt for a snail or two.