Keeping a group of female bettas together sounds simple on paper. Toss a few fish into a tank, add plants, done. Reality is a bit different. Female bettas can live together, but only if the space, layout, and stocking numbers are planned properly. Get the math wrong and the tank turns into a boxing ring.

The Ideal Number of Bettas for a 20 Gallon Tank

In a 20-gallon aquarium, the ideal number of female Bettas is 5 to 7.

This specific range is based on the biological need to diffuse aggression. Bettas are naturally territorial. If you keep only two or three, a dominant "Alpha" will likely emerge and focus all her energy on bullying the one or two subordinates. This constant harassment leads to chronic stress, which suppresses the immune system and often results in the death of the weaker fish.

By maintaining a group of at least five, the Alpha’s attention is spread thin. If she feels the urge to chase, she has several different targets, meaning no single fish bears the brunt of the aggression. This allows for a more stable social "pecking order" to form.

Helpful Tip: Try to stick to an odd number of fish. While it sounds like a superstition, many hobbyists find that odd numbers help prevent the fish from pairing off and fighting one-on-one.

Choosing Between 20 Gallon Long and 20 Gallon High

When you go to the store, you will likely see two types of 20-gallon tanks: the "Long" and the "High." For a Betta sorority, the 20-gallon Long is much better.

Bettas are shallow-water fish by nature. They like to swim back and forth more than up and down. A "Long" tank provides more "floor space" for the girls to claim their own little corners. It also makes it much easier for them to reach the surface to breathe, which is important since Bettas have a special organ that lets them gulp air from the top of the water.

Tank Setup Tips for a Peaceful Sorority

If you’re keeping female bettas in a 20-gallon tank, here’s how to set it up for long-term success:

1. Break Line of Sight

Use plants, driftwood, rocks, and decorations to break up open space. This helps each fish feel like it has its own area and reduces chasing.

2. Use Live or Silk Plants

Soft plants like Java Fern, Anubias, and Amazon Sword are great. They provide shelter and don’t damage delicate fins.

3. Create Multiple Hiding Spots

Caves, floating plants, and hollow logs are lifesavers during conflicts or if one female needs to lay low for a while.

4. Go for a Long Tank, Not a Tall One

More horizontal swimming space means more room for territories. A 20-gallon long is much better than a 20-gallon tall for this purpose.

5. Keep Conditions Stable

Stable water temp (78–80°F), gentle filtration, and weekly water changes are a must. Ammonia spikes in a sorority setup can quickly lead to stress and disease.

Because you are housing 5 to 7 fish in a 20-gallon space, your filtration needs to be reliable. However, Bettas are not fans of strong currents. A sponge filter or a power filter with a "baffle" to slow the flow is ideal.

Keeping the water clean and warm is the best way to prevent aggression, as stressed fish are much more likely to lash out.

How to Manage the Group Dynamic and Social Hierarchy

The way you introduce your Bettas is just as important as how many you have. The best method is the Simultaneous Introduction. If you add one fish today and another next week, the first fish will think she owns the whole tank and will treat the newcomer like a trespasser. 

Therefore, use the Simultaneous Introduction method:

1. Set up the tank with all plants and decor first.
2. Purchase all 5 to 7 females at the same time.
3. Float them in their bags to acclimate to the temperature.
4. Release them all into the tank at once.

By doing this, no fish has a "home-court advantage." They will all be equally confused and focused on exploring their new surroundings rather than defending an established territory.

When Should You Remove a Fish

Even with a perfect setup you have to be a referee. You will see some display behavior during the first few days like puffing out gills. This is normal behavior as they decide who is the boss. However you should look out for these red flags.

• Tattered fins mean the bullying is too intense.
• Stress stripes or dark horizontal lines on the body mean she is very unhappy.
• Hiding constantly behind the heater means she is being bullied.

Always have a Plan B like a separate 5 gallon tank just in case one of the girls does not want to play nice.

Build Your Sorority with Tropicflow

Ready to start your tank? At Tropicflow we are passionate about providing the healthiest and most vibrant fish for your aquarium. Whether you are looking for a peaceful group of females or a stunning show-quality male we have something for every aquarist.

• Start your sorority by browsing our beautiful collection of Female Betta Fish.
• Find a centerpiece by checking out our spectacular Male Betta Fish.

Visit us today to find the perfect addition to your tank!