Bettas and Mollies as tank mates: Is it possible?

Finding good tank mates for your betta isn’t easy. Bettas are aggressive and territorial fish. Also, they can live by themselves just fine. But there are cases where bettas are fine living in a community tank. Mollies are known to be low-maintenance fish with various species to choose from. But can they live together?

In this post, we will share some facts about mollies like their appearance, diet, lifespan, tank setup, behavior, and breeding. We will also talk about whether mollies and bettas can live together.

Can bettas and mollies live together?

Mollies and bettas have very different temperaments. Initially, mollies shouldn’t be housed with aggressive fish. But, if the proper tank arrangements are made, it should be alright for mollies and bettas to live together.

Mollies overview

Molly fish or just mollies are freshwater fish belonging to the Poeciliidae family. All species in this genus are mollies but the Endler’s livebearer. They are native to the Southern United States down to Central America in the Yucatan peninsula in Mexico. Although they’re freshwater fish, they can be found venturing into brackish estuaries sometimes. They make an active and social group.

Mollies appearance

Mollies have a flattened body and a triangular-shaped head. From the mid-section of the mollies’ body decreases to a narrow point at the snout. On the opposite end, the body tapers towards the base of the fan-shaped tail.

Male mollies are smaller and have a pointy anal fin, which in the female it’s broad and fanned. Female mollies can have a visible gravid spot, where they carry their fry during pregnancy. 

Captive mollies have interbred over centuries, resulting in a variety of colors like black, orange chocolate, white with black hues, gold dust, and even an albino species. They also have different fin shapes.  There are around 39 different species of mollies. Some of them are:

  • Balloon mollies
  • Sailfin mollies
  • Black mollies
  • Dalmation mollies
  • Lyretail mollies
  • Gold Doubloon mollies
  • White mollies
  • Common mollies

Avoid getting balloon mollies. Although different and cute, they were selectively bred to have such a balloon body. This resulted in mollies with scoliosis. The misshapen spine makes it difficult for them to swim, and their organs are compact in their body making them prone to constipation. It’s a lot of unnecessary suffering for this poor molly.

Most adult mollies can grow up to 4.5 inches (11.4 cm). Sailfin varieties can get to 5 or 6 inches (12.7 to 15.2 cm). These fish can live from 2 to 5 years.

Mollies behavior

Mollies are easy-going, peaceful fish that usually do well in community tanks. They are shoaling fish, so you must have at least a group of four fish to keep them happy. Mollies also like to explore the tank and school together. However, a shoal is mostly composed of female mollies since males can often harass them.

Although mollies are not known to be aggressive, there are occasions where they can display signs of aggressiveness. These can happen when you have a large number of males together or during courtship.

Mollies are hierarchical. Thus, they can fight to know who will be the alpha male in the group. They usually don’t attack other fishes, although there is a small chance of fin nipping occurring.

Male mollies can harass the females when it’s time to breed. This can cause stress in females so, make sure the females outnumber the males to minimize such behavior.

These fish are peaceful most of the time, but they can display signs of aggression if the tank is overcrowded or shared with aggressive tank mates. Hence, it’s important to offer them a big tank as well as suitable tank mates.

Mollies diet

Bettas are carnivorous fish while mollies are omnivorous. They can eat high-quality fish pellets and flakes, frozen meat, and live food such as daphnia, bloodworms, and mosquito larvae. Additionally, mollies can eat blanched vegetables like spinach, lettuce, zucchini, and graze on algae as well.

Both fishes can get competitive when it comes to feeding. To limit this problem, you can spread fish food at one end of the tank for mollies, and at the other end, some pellets to your betta. This way all fishes will be properly fed.

Mollies breeding

Throughout their lives, mollies can spawn new fry several times. These fish are livebearers. So, instead of laying eggs, the female will hold them in its ‘gravid spot’ until the fry is ready to hatch. Then, she releases a fully formed and free-swimming fry into the water.

If you want to breed mollies, the environment should be controlled to increase the chances of the fry surviving. Have a separate breeding tank with water temperature up to 78 F (25.6 °C).

Place the pair in the breeding tank. The males will court the females before they are allowed to fertilize the eggs. The gestation of the fry takes about 35 to 45 days. When the female is about to give birth, it should be placed in a breeding box.

Mollies don’t display any parental instincts, and they can try to eat their fry. Breeding boxes keep the female contained so the fry is able to slip down through the bottom of the box. You can feed the fry infusoria or powdered fish food. They can be weaned off with baby brine shrimp until they can eat their regular diet.

Adult mollies can give birth to as many as 100 babies at once. So, if you don’t want to have extra fish in your tank you can let the fry become live food to other fishes or you can limit yourself to having just one gender of mollies in your tank. Keep in mind that if you acquire a female, it might come to your tank already bearing fertilized eggs.

The perfect tank setup for mollies

Although there are a lot of sources that state that mollies can do well in a 10- gallon tank, a bigger tank will be better.  A 20-gallon tank will provide more room for your mollies to school, keeping their stress level to a minimum. A larger tank will also be better to support the shoal’s waste which will prevent ammonia spikes in your water tank.

Regarding water parameters, mollies can thrive in temperatures between 68 to 82 F (20 to 27.8 °C). The pH should be ranging from 7.0 to 7.8. The water hardness should be from 20 to 30 KH. As for lighting, they are fine with standard light. Make sure you consider other tank mates’ and plants’ light requirements if you do have them in your tank.

Mollies do need a powerful filtration system as they produce a lot of waste. A small shoal can produce enough waste to spike ammonia and nitrate to high levels, which can make your mollies ill. Molly disease or ‘the shimmies’ are caused by high levels of ammonia in the tank. Having additional sponge filters is also great. Mollies can also have Ich, bacterial infections, flukes, and parasites.

The best way to keep your mollies disease-free is to monitor the water conditions regularly. About 25 to 35% of the tank water must be changed weekly to keep the ammonia and nitrate levels stable.

These fish thrive with decor that mimics their natural habitat. Thus, having natural plants and hiding places is a must. The best substrate for mollies is sand or gravel, as they spend most of their time in the middle and upper parts of the water column. You can also add rocks, caves, and driftwood, but make sure they have enough space to swim. 

Making mollies and bettas live together happen

Mollies are peaceful fish, unlike bettas that can be aggressive. But it all comes down to your fish’s temperament. If your betta is rather calm and does well in a community tank, then you shouldn’t have a problem. If your betta is aggressive, it’s better not to add your mollies in its tank.

Your mollies may also get stressed if your betta keeps flaring at them. They might even fin-nip your betta. So, be very attentive to both fish’s behaviors. One thing to avoid this is to add your betta to your mollies’ tank and not the opposite. This way your betta won’t feel like another fish is invading its territory.

Female bettas are less aggressive than males and they could be more suitable tank mates for mollies. If you choose to have a sorority of female bettas in your tank, make sure to have a bigger tank to accommodate bettas and mollies.

Lastly, mollies can compromise to a pH of 7.0 and a temperature of 78 F (25.6 °C) to accommodate the betta’s needs when sharing a tank together.


In the proper tank setup and taking into consideration the temperament of your betta, mollies can be a great addition to their tank.

Mollies can grow up to 4.5 inches (11.43 cm). If you have a sailfin molly, it can grow up to 6 inches (15.24 cm), whereas bettas grow up to 2.4 to 3.1 inches (6 to 8 cm). Hence, their community tank should have at least 20-gallon volume for a shoal of 4 mollies and a betta.

Bettas and mollies have similar diets. You can avoid confrontation over food by feeding each fish on a separate corner of the tank. Also, add blanched vegetables to your mollies’ diet. If you have some algae build-up in your tank, mollies will graze on them. Nevertheless, they won’t do the whole clean-up.

Mollies are highly adaptable and they can adjust to a temperature (78 F or 25.6 °C), and a pH (7.0) that is best for your betta. However, the tank must have a powerful filtering system to filter the water and avoid ammonia and nitrate levels increase, which can get your mollies sick.

Mollies are livebearer fish and they mate several times during their life. If you don’t want an overcrowded tank, you can opt for having only females or have a thought-out plan to deal with the extra fry.

Mollies are peaceful and unlikely to attack your betta. They can fight among themselves to establish a hierarchy or harass females during courtship. However, if your betta starts attacking the mollies, they might fin-nip your betta. You can try to add a female betta instead of a male one or even add the betta into the mollies’ tank so it won’t feel that other fish are entering its territory. 

Bettas and mollies can live together peacefully if we carefully plan for a community tank and consider the temperament of each fish. With such a great variety of mollies and a nicely decorated tank with plants and hiding spots, your betta and mollies will be fine together. Did you like this post? Leave us a comment below! 


Barrington, K. n.d. The right way to care for Betta fish. 45 p.

Glass, S. (1997). Mollies: Keeping & Breeding Them in Captivity. Tfh Pubns Inc. 64 p.