How many Betta Fish per Tank?

You can keep several betta fish in the same tank, but you need to follow these two simple rules -

Make sure the tank is large enough and that water quality is adequate.

Never keep more than one betta male in the same fish tank.

Male betta fish are beautiful but notorious for their aggressiveness towards other male bettas. They are even known as the "Siamese Fighting Fish" because of their habit to attack any other present betta male. It is true that male bettas will even attack their own reflection in the mirror, but please don't test this by placing a mirror next to your fish tank. Even if your fish sustains no physical injuries, having to constantly be involved in this mock fight causes the fish too much stress.

It is possible to keep more than one male betta fish in the same fish tank provided that the males are separated in their own enclosures, also known as betta fish condos. These are see-through plastic cages that keep the fish separated while allowing them to see each other. While preventing actual fights and injuries from happening, the fish may still be stressed out from the presence of a competitor in their territory, so this is not a recommended setting for any long period of time.

Surprising as it may seem for unexperienced owners, fish can have their own individual behavioral traits. Some fish, whether male or female, simple tend to be more aggressive then others and may harras their tank mates (betta fish or other critters). If you have a particularly aggressive betta fish you may have to consider seperating it from the rest of the inhabitants of your aquarium.