Will Betta Fish Kill Mollies: Explained

Will Betta Fish Kill Mollies

Betta fish and Mollies are two popular aquarium fish that are often kept in the same tank. While both are peaceful fish, there is a concern among aquarists that Betta fish may kill Mollies due to their aggressive nature. In this article, we will explore will betta fish kill mollies and provide some tips for keeping them together.

Will Betta Fish Kill Mollies?

Reasons Mollies Maybe Good Tank Mates for Bettas

Mollies and Bettas are both popular species of freshwater aquarium fish, and while there is a concern about Bettas attacking Mollies, there are some reasons why Mollies may make good tank mates for Bettas.

Hardiness and Tolerance

Mollies are generally hardy fish that can tolerate a wide range of water conditions, which makes them easier to care for than some other species. They are adaptable to different pH levels, salinity levels, and temperature ranges to live in various aquarium environments.

Peaceful Nature

Mollies are typically peaceful fish that can coexist with other species. They are unlikely to attack or harass other fish, which makes them good tank mates for Bettas, which are also relatively peaceful. However, it’s important to note that Mollies with long, flowing fins may trigger aggressive behavior in Bettas, so it’s best to stick to short-finned Mollies.

Active Swimmers

Mollies are active swimmers and enjoy exploring their environment. They often swim around the middle of the tank, which can create an interesting contrast to the top-dwelling Bettas. Having Mollies in the tank can add diversity to the aquarium and keep it lively and exciting to observe.

Reasons Mollies May Not be Good Tankmates for Your Betta

While Mollies can make good tank mates for Bettas in certain situations, there are some reasons why they may not be the ideal companions.

Aggressive Tendencies

One of the main reasons Mollies may not make good tank mates for Bettas is their aggressive tendencies toward each other. Mollies can be territorial and may try to establish dominance over other fish in the tank, which can lead to conflicts with Bettas. Additionally, Mollies with long, flowing fins may trigger aggressive behavior in Bettas, which can cause stress and potential harm to the Mollies.

Different Water Requirements

Mollies and Bettas have different water requirements, making it challenging to keep them both in the same tank. Mollies prefer a higher salinity and harder water, while Bettas prefer soft, acidic water. This difference in preferences can make it challenging to maintain a suitable environment for both species.

Can Molly Fish Live with Betta: Tank Setup

Can Molly Fish Live with Betta Tank Setup

If you’re planning to keep Betta fish and Mollies together, you’ll need to ensure that the tank is set up correctly. Here are some tips for creating a suitable environment for both fish species:

  • Tank size: A 20-gallon tank is recommended for keeping Betta fish and Mollies together. This will provide enough space for both fish to swim and establish their territories.
  • Decorations: Providing ample hiding spaces in the tank can help reduce stress for both fish. Live plants, driftwood, and caves are all great options for creating hiding spots in the tank.
  • Water parameters: Both Betta fish and Mollies require similar water parameters. The ideal temperature for both species is around 78-80°F, with a pH between 7.0-8.0. It’s essential to regularly test the water quality to ensure that the tank is adequately cycled and that ammonia and nitrite levels are safe.

Feeding Betta Fish and Mollies

Betta fish and Mollies have different dietary needs, so it’s vital to ensure that both fish are fed appropriately. Mollies are omnivores and will eat both plant-based and meat-based foods. A diet of high-quality flake food, supplemented with occasional treats of live or frozen food, will provide a balanced diet for Mollies.

Betta fish, however, are carnivores and require a high-protein diet. A diet of high-quality Betta-specific pellets, supplemented with occasional treats of live or frozen food, will provide a balanced diet for Betta fish.

When feeding both fish, it’s crucial to ensure that each fish receives an appropriate amount of food. Overfeeding can lead to health issues for both fish species, including obesity and digestive problems.

How to Make Mollies and Bettas Compatible

How to Make Mollies and Bettas Compatible

Introducing mollies and bettas in the same tank can be challenging since both are territorial and can display aggressive behavior toward each other. However, there are ways to minimize aggression between these fish and create a peaceful coexistence in the aquarium. Here are some tips to lessen aggression between mollies and bettas:

  1. Tank size and layout: The tank size should be large enough to provide ample swimming space for both fish. Bettas are known to be territorial and need their space, so it’s important to provide hiding spots and plants to break the line of sight. Mollies are active swimmers, and they need open areas to swim. So, providing a well-planted aquarium with hiding spaces and open regions can help reduce aggression.
  2. Introduce fish gradually: When introducing new fish to the tank, it’s essential to do it slowly to reduce stress and aggression. Start by adding the mollies to the tank first and let them get accustomed to their new surroundings. After a few days, introduce the Betta to the tank. This will give both fish time to acclimate to each other’s presence.
  3. Feed the fish separately: Feeding the fish simultaneously can cause competition and aggression. Therefore, feeding the fish separately is best to avoid conflicts. You can use a fishnet to remove the Betta from the tank during feeding.
  4. Maintain water quality: Poor water quality can lead to stress and increased aggression. Therefore, it’s important to maintain good water quality by performing regular water changes and keeping the tank clean.
  5. Monitor the fish: Keep an eye on the fish’s behavior and look for any signs of aggression. If you notice any signs of aggression, separate the fish immediately. A separate tank or aquarium divider can keep the fish apart.

Can Female Betta Fish Live with Mollies?

Introducing female betta fish to a tank with mollies can be feasible, but it still requires careful consideration. Female bettas are generally less aggressive than their male counterparts, but they can still display territorial behavior toward other fish. Mollies are active and peaceful fish that can tolerate a wide range of water conditions, making them suitable companions for female bettas.

However, as with any fish compatibility, individual temperament and tank size play a crucial role. Introducing the mollies first and then adding the female Betta to the tank is recommended. It is essential to keep an eye on the fish’s behavior and separate them if any signs of aggression occur. Providing a well-planted aquarium with hiding spaces and open areas can help reduce aggression and promote a peaceful environment for both fish species.

Different Types of Mollies

Mollies are popular and colorful freshwater fish that come in various types and colors. Here are some different kinds of mollies, along with their distinctive characteristics.

  1. Black Molly: As the name suggests, black mollies are black, and they have striking fins that are typically larger than those of other mollies.
  2. Dalmatian Molly: Dalmatian mollies are characterized by their white and black-spotted body. They are a popular variety due to their unique and eye-catching appearance.
  3. Balloon Molly: Balloon mollies have a round body shape, which gives them a distinctive appearance. They are available in various colors, including white, black, and orange.
  4. Sailfin Molly: The sailfin molly is named after its oversized dorsal fin, which resembles a sail. They are an attractive variety and are available in many different colors.
  5. Lyretail Molly: Lyretail mollies have a flowing and elongated tail fin that resembles a lyre. They are available in a range of colors, including orange, black, and white.
  6. Orange Molly: Orange mollies are a bright and eye-catching variety in many shades of orange.
  7. Green Molly: Green mollies have a unique and distinctive coloration ranging from light green to deep, almost black.
  8. Gold Dust Molly: Gold dust mollies have a golden-yellow body with a unique speckled pattern that gives them a sparkling appearance.
  9. Peppermint Balloon Molly: Peppermint balloon mollies have a unique and distinctive design of white and red stripes that provide them with a peppermint candy-like impression.

Why You Should Avoid Balloon Mollies

Balloon mollies are a variety of molly that have been selectively bred to have a rounded, balloon-like body shape. While these fish may be appealing to some due to their unique appearance, there are several reasons why they should be avoided. First and foremost, their balloon shape is unnatural and can cause health problems such as swim bladder issues and difficulty swimming.

This can lead to a reduced lifespan and a lower quality of life for the fish. Additionally, balloon mollies are more prone to developing tumors and other health problems than different varieties of mollies. Lastly, balloon mollies can have difficulty breeding due to their distorted body shape, which can cause problems for those who wish to breed mollies. For these reasons, it is recommended that aquarists avoid balloon mollies and choose other, healthier varieties of mollies for their aquariums.


In conclusion, while it is possible to keep Betta fish and Mollies together in the same tank, there is a risk that they may kill Mollies with long, flowing fins due to their aggressive nature. It is recommended to keep Mollies with short fins, provide ample hiding spots in the tank, and closely monitor the fish for signs of stress or aggression to minimize this risk. As with any new tank setup, it’s important to make adjustments as necessary to ensure the health and well-being of both fish species.

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