How Many Molly Fish Should You Keep Together In The Tank?

Are you considering having Molly fish in your aquarium lately? If yes, I am sure you would love to see many of them swim and thrive together. However, checking their appropriate counts in the tank is significant to keep the tank environment balanced. So, how many Molly fish should you keep together precisely?

You need to keep a group of 5 to 6 Molly fish together in any tank size. Each Molly fish of different species require at least a 3-gallon tank at a minimum. So, determine their existing number with the particular aquarium size while putting them together. Always remember to keep them either in pairs or groups. 

Note that not all species of Mollies are the same size. So, a small group of common Molly fish together is fine to stay in a minimum of a 20-gallon tank. Meanwhile, Sailfin or Lyretail Mollies require at least a 30-gallon tank to fit their small group finely.

Let me explain it further in the article below. I hope you find what you are looking for!

How Many Molly Fish Should You Keep Together?

If you want to get Molly fish for your aquarium, it is essential to note their counts precisely. This is because the more or less number of Mollies in a specific tank impacts their living.

So, it is best to form a group of 5 to 6 Molly fish together while keeping them in a tank. Only a small group is necessary to settle the fish and make them feel comfortable and secure in their tank. But, you can still go for more of them, depending on your tank size. 

If you are unsure about the correct tank size for Molly fish numbers, you can also keep them as a pair. 1 to 2 pairs of these fish are also suitable to put together in a tank, if not in groups. Of course, a duo of Molly fish living together is better than living solely! 

But possible, try to keep Mollies in a small school of 5 to 6. A minimum needed group count is essential to make their life pleasant and thrive better.

How Many Molly Fish To Keep Together In A Community Tank?

If you are unaware, let me tell you that your Mollies can be good companions when kept in a community tank. So, you can certainly add them to it with other compatible tank mates.

The number of Mollies to keep together in a community tank depends on the tank size. But it is for sure, here, the Molly fish counts will be fewer than in their only specific tank.

It happens as you have to fit other fish with them in a community tank, which certainly decreases the number of Molly fish.

For example, in a 20-gallon tank, you can keep up to 6 Molly fish together of 3 inches. But in a community tank of the same size, a small group of Mollies having 5 to 6 of them cannot fit in it. So you can keep up to 4 Mollies only in a 20-gallon community tank.

Plus, the count gets even fewer if you have Sailfin or Lyretail Mollies. 

Here, if you increase their numbers, the tank gets overcrowded, causing problems for the fish. So believe me when I say Overstocking the aquarium is never, I repeat NEVER, a good idea. It suffocates and stresses them a lot, which can trigger Mollies’ aggression, and mind you, molly fish can get much more aggressive than you originally imagined.

Thus, I advise you to analyze your community tank size as it helps define the Mollies count.

Why Is It Essential To Keep Molly Fish Together?

You can see your Molly fish thriving at best when you keep them together in a group.

Precisely, it is essential to keep Molly fish together because:

  • It makes them feel secure, relaxed, and pleasant in the tank.
  • The breeding stage passes without any aggressive issues when their species is around.
  • The aggression and attacking behavior of Mollies seem unlikely when kept together.
  • They take not much time to adapt in the tank without distressing.
  • They stay active, happy, and satisfied in the tank.

How Many Molly Fish Can My Tank Accommodate?

If you are worried about whether the tank you own can accommodate all your Mollies or not, then here is what you should know! The question always lingers, doesn’t it? How many molly fish to keep in your 5, 10, 20, 30, or more gallons tank? We don’t want to play the overstocking game, now do you?

There is a general rule of thumb for fish that says; 1-inch fish requires a 1-gallon tank. Here, a common Molly fish increases up to 3inches. It means the fish need a 3-gallon tank at a minimum.

However, if you have Sailfin or Lyretail Mollies, they tend to grow longer than a Common Molly. For example, they might increase up to 5 inches long. Thus, they at least require a 5-gallon tank each.

You can calculate the number of Mollies your tank can accommodate with this rule. In case of any confusion, you can remember the following method: 

The number of Molly fish= Tank size divided by the maximum length of Molly fish.

For example, you have a 20-gallon tank size, and the Molly fish is 3 inches long (mostly a Common Molly). Now, using the method, calculate; 20/3=6.67.

Following, you can accommodate up to 6 Mollies together in a 20-gallon tank.

If your Mollies are 4 or 5 inches long, you can now find their accurate number to accommodate respectively by analyzing the tank size.

Overall, only your tank size determines the number of Molly fish that can accommodate it.

What Is The Minimum And Maximum Tank Size Suitable For Mollies?

Not to forget, Molly fish should be in a group together to live happily in the tank. The more the fish, the more they flourish.

So, it is essential to keep them in a 20-gallon tank at a minimum. This tank size is appropriate to get 5 to 6 of the Molly fish in a group and a few more aquarium decorations. You can even keep them in a pair with the same minimum tank size.

However, for longer Mollies like Sailfin and Lyretails, the minimum size specified is a 30-gallon tank. In a less than 30-gallon tank, they cannot fit properly as a group of 5 to 6. Or, you will have to reduce their counts and keep up to 4 of them only.

Regarding the maximum tank size, there are no particular limits. There will be more added Mollies in a bigger tank, plus they will get enough tank space too. But be careful while making the Molly fish count larger because the difficulty of tank overcrowding might form if you add them countlessly. 

What To Avoid In The Tank While Keeping Molly Fish Together?

There are lots of benefits for Mollies that you can provide by keeping them accurately in the tank. Meanwhile, there are some factors that you must know and avoid in their tank.

Thus, things that you must avoid in the tank while keeping Molly fish together are: 

Tank Overcrowding

Yes, it is essential to keep a group of Mollies together for their comfortable life in the aquarium.

But sometimes, tank overcrowding might happen if you don’t analyze the fish counts with the respective tank size.

Adding numbers of Molly fish in the tank without considering the fish tank creates tank overcrowding.

Such a situation causes stress and suffocation to fish where they feel highly unpleasant and uncomfortable. It is not a healthy sign for your Mollies!

Thus, it is significant to make a group of Molly fish by seeing how many can the specific tank accommodate. It prevents tank overcrowding.

More Males And Fewer Females Ratio

Whenever you keep Mollies in a group, limiting the male Mollies ratio to females is essential.

Do not keep more males and fewer females in a tank together. Since male Mollies are slightly aggressive when breeding, they are likely to fight among themselves. 

Also, if the males are more in the tank, these molly fish will chase and bother females because of the mating induced. They tend to get aggressive and harsh if they can’t breed due to fewer females.

So, to avoid this issue in the tank, keep more females and fewer males in the tank. The ratio where male Mollies are more usually makes the tank situation unhealthy since they are likely to fight and chase a lot. Also, identify if your molly fish is male or female before purchasing them or keeping them in the tank.

Aggressive Tank Mates

Mollies are peaceful, active, and friendly fish. They usually get along with most fish species that have similar traits alike. However, they don’t get along with fin nippers and aggressive species like Bettas and Cichlids. You might even find your molly fish happily eating the food your drop for bettas, thus the dispute.

Aggressive fish species aim to chase and bully Mollies in the tank. This situation will distress your Mollies, impacting their health and behavior. Keeping Mollies with such tank mates can make their lives toxic and weak.

Therefore, avoid keeping your Mollies with aggressive tank mates that can harm your fish. And don’t act shell-shocked if you find molly fish nipping fins of bettas in the tank.

Can I Keep Molly Fish Alone In A Tank?

Your Mollies are not just peaceful but social, making good companions in a community tank. Now, imagine such a social fish living solely in the aquarium! But, of course, it is unseemly.

Therefore, you cannot keep Molly fish alone in a tank. When there is no fellow for your fish, the fish feel uncomfortable and uneasy. 

Slowly, they may lead to aggression, improper diet intake, no activeness, etc. This burden will make Molly mentally and physically weak. As a result, you may witness your fish getting ill and battling many molly fish diseases.

Also, due to the absence of their species, Mollies lack a mating partner. Therefore, it makes the fish even more offensive since its mating inducement remains unfulfilled.

Thus, you may find your fish look sound from the outside when kept alone in a tank. But in reality, Mollies battles a lot, issuing from mental and emotional trauma.

So, you cannot keep your Molly fish alone if you wish to see them live long and thrive. 

Tank Mates For Molly Fish

Since Mollies have polite behaviors and friendly attitudes, you certainly can consider finding tank mates for them. 

However, remember not to mainly include fin nippers and aggressive tank mates like Bettas and Cichlids. Such fish species can chase, attack, and harm your Mollies.

So, you must look for such tank mates that share similar traits to Molly fish. It will make them compatible and live together peacefully, without harming one another.

Hence, some tank mates that you can pick for Molly fish are:

Essential Tank Conditions For Keeping Molly Fish

While you plan to keep Molly fish together, few tank conditions are essential for them. Instead, these requisites make their life easy and wholesome when maintained correctly in the tank.

Thus, I have accumulated the ideal water parameters for your molly fish below. Give it a quick glance, will you?

  1. Manage absolute water parameters for Mollies in the tank. For example, keep 70 to 80F water temperature, pH from 7.5 to 8.5, and 20 to 30 dGH of aquarium water hardness.
  2. Add some live plants to the tank to provide hiding space for your Mollies. It also helps in the oxygenation process in the tank.
  3. When you add plants to the tank, lighting gets requisite in the aquarium. Thus, maintain at least 8 to 10 hours of tank lighting daily. 
  4. Always keep the tank environment clean and pure for letting your Mollies thrive and endure better. Remove dead plant pieces, leftover fish diets, fish excretes, and other irrelevant elements noticed in the tank. You can use a spinner or a net for cleaning up.
  5. Perform 20% to 25 % aquarium water changes every week to maintain the water quality and prevent filthy water contamination. Be careful and execute this whole process without disturbing your fish. Otherwise, it might stress them.

Frequently Asked Questions

I have also collected some of the FAQs and answered them to make it easier for you.

Can I Keep Male Molly Fish Only?

No, you cannot keep Molly fish only in the tank. This is because males are somewhat aggressive and competitive. Thus, they might end up fighting among themselves. Also, the lack of female Mollies may lead to more aggression due to unfulfilled mating inducement.

How Many Molly Fish Can I Keep In A 5-Gallon Tank?

You can keep only one Molly fish in a 5-gallon tank. However, as living alone can be unsafe for them, I would suggest you not keep them in such a small-sized tank.

Can I Keep 3 Mollies Together?

When you keep 3 Mollies together, it makes them tough to make a pair. Even if they make it, the other one would be left out alone. So, you cannot keep 3 Mollies together in a tank.


Remember to always look for the correct count of Mollies to form their group in a specific tank. I know it might puzzle you a little, but of course, it is vital.

Hence, you can keep 5 to 6 Molly fish together in at least set up a 20-gallon tank. For Sailfin or Lyretail Mollies, a 30-gallon tank is essential to form a group of 6. If you have a smaller-sized tank than mentioned, at least keep them in a pair.

I hope this article was helpful for you to find the answer to your query. 

Keep your Mollies safe and healthy!