How big of a tank do you have to have for a Betta fish?

One Is NOT the Loneliest NumberNo tank size is "best". Unfortunately, no matter how much you love those beautiful betas, one is definitely NOT the loneliest number for these guys.

Whether male or female, ALL BETAS SHOULD BE EXPECTED TO FIGHT. Betas are highly aggressive with one another, and are very territorial. A period of mating is not an exception, and can still result in an injured fish.

As a general rule, one beta will be healthier NOT sharing its life with another beta. Forcing two betas to share an environment may result in severe and even life-threatening injuries.

No matter how large the tank, eventually the betas will inevitably find their way into the same area, and when they do, you'll have Mortal Kombat 3 in your fish tank.

Moreover, even if they merely saw one another from far, far, opposite sides of the tank, it's extremely (VERY!) likely that at least one of the two betas (if not both) would actually find the other enough of a threat to put itself immediately into the other's space and engage in aggressive activity.

If you're asking because you really want to own more than one beta, there are other solutions that are slightly preferrable (although some may still be somewhat upsetting to the betas).

If you really, really just want more betas, the best solution is to buy those small plastic containers sold at places like Petsmart, containers that are meant for betas; the single-celled containers are a less stressful environment for the betas, because you can separate them so they won't antagonize each other.

However, stores also sell larger containers with a divider in the middle, which leaves room for two betas.

Large glass fish bowls are also a novel idea, because they have plenty of room for pretty rocks, air pumps, castles, and the like.

If your main concern is about your beta's happiness or you wonder whether it is lonely, ask me for more information about things you can add to a beta's tank for recreation (such as an air pump, live plants, structures to hide in, etc.). There are quite a few things that can very much add to your beta's quality of life.