One of the most common pet fish, Molly fish, is also a difficult species among the common species if you don’t know its requirement. As small and delicate as it looks, it requires great care too. Today, we will be talking through how many molly fish you can put in your tank and how you can provide them with a good environment to survive.
One inch of fish requires one gallon of water to survive. So, for an adult molly fish, 3 inches in length requires 3-Gallon of water. Let’s suppose One-Gallon of your tank volume is covered by the decorations leaving you 9 gallons behind. So, that’s (10-1)/3=3; you can add three molly fish in a 10-gallon tank. Similarly, you can keep 6 and 10 mollies in 20 and 30-gallon tanks respectively.
People usually add decorative items like aquatic plants, gravel, driftwood, and many more, to make their tank look pretty. However, many of us don’t realize that these accessories take up the aquarium space, decreasing the water availability for its residents.
I am not giving you any advice not to keep decorative items, but it will help you calculate the area it takes while calculating the fish’s space. So, please dive in to know all about the tank size and number of molly fish you can keep in it.
All About Molly Fish Size: A Short Description
A community fish from the genus Poecilia, a molly fish, is the one most of us have seen at least once or have been petted at least once by the keepers.
This genus has about 39 species of mollies, but only three of these species are available in the aquarium trade. Varying in shapes and colors, sizes ranging from 2 to 3 inches, and peaceful, mollies have an attractive appearance with a lifespan of up to 5 years.
The Sailfin Mollie is undoubtedly the most beautiful and exotic fish among the species. Originating from Mexico, Central America, and the northern parts of South America, these small-sized tropical fish are hybridized for a more colorful and better specimen.
Another differentiating characteristic is the body size; the females can grow up to 4.5 inches, but the males only up to 3 inches. The most common mollies for home aquariums include Black Molly, Sailfin Molly, and Lyretail Molly.
Tank Size of Mollies
As easy as Mollies seem to be kept, you need to ensure certain tank requirements to keep your small babies healthy and happy. These tiny creatures have a bland diet. They feed on bits of food, flake food, and live or frozen food like bloodworms, brine shrimp, and daphnia.
It would help if you were very cautious about the number of Mollies you keep in the given tank size and not overcrowd the tank. I repeat, DO NOT overcrowd the Mollies in your tank. It can lead to fights between the breed themselves.
One inch of a molly requires a gallon of water. Depending upon the size of the species, you need to choose your tank size. For four of the mollies, 10-gallon water will work. But if you have Sailfin mollies, you would require about 30-gallon of water for four of them [may vary according to the size]. Tall aquariums are recommended for them.
How Many Molly Fish In A 5-gallon Aquarium?
Since overcrowding is specifically suggested to avoid and create the landscape using substrates, live plants, rocks, and caves, space occupied by the decorative also needs to be considered. So, it would be wise of you to keep only one molly in a 5-gallon aquarium.
But from my personal experience and knowledge, I suggest you rather not keep your molly alone.
How Many Molly Fish In A 10-gallon Aquarium?
With the growing tank size, the number of mollies you can keep also increases. Sounds exciting? It is, but it doesn’t give you the liberty to add many as you want. The numbers have to be limited. In a 10-gallon aquarium, you can add a maximum of 3 Mollies.
Say one molly is 3 inches, so 3-gallon of water for that fish only. So, if they have a standard size of 3 inches, then 3×3= 9-gallon of water for 3 Mollies and the remaining 1 gallon for the accessories that take up the tank space.
We can see that the number of Mollies put in the 10-gallon can vary according to the size. The purpose of allocating the water as per the size of the fish is because they need a huge space to swim.
How Many Molly Fish In A 20-gallon Aquarium?
In a 20-gallon aquarium, 20/3= 6.67. We can see that up to 6 Mollies of 3 inches can be added. If the molly fish is 4 inches, you can add 20/4= 5 Mollies in a 20-Gallon tank.
But to add five fish would be compact, so reducing the number to 4 Mollies is advised. If your Mollies are 2 inches, you can add 9 Mollies. But the size of each molly doesn’t have to be the same.
How Many Molly Fish In A 30-gallon Aquarium?
Calculating similarly, you can add up to 30/3=10 Mollies in a 30-gallon tank. But if you are choosing a Sailfin Molly, you will require a 30-gallon aquarium, as they need a lot of space to swim.
I believe that you have noticed how I have been suggesting you keep the Mollies in even numbers. It is better to keep them in pairs, preferably keeping the number of both gendered Mollies the same. Or follow the rule of thumb, “two females per male,” to reduce the chances of bullying.
How Many Molly Fish Can Your tank Accommodate?
The number of Mollies that your tank can accommodate depends on your tank size. So, you can calculate the number of Mollies you can keep in your tank by yourself for your convenience.
The trick to finding this out is “Size of the tank ÷ Max Length Of a Molly Fish = Number of Mollies.”
In this, we first choose the size of the tank. Then, we take the number of Molly fish we want to add or suppose a certain number. Take either two females per male or an equal number of both genders. Then, please measure the length of each of them; it is easier to round off the decimals. Next, add the length of all the fish. Then divide the size of the tank by the sum of the length. Finally, subtract the result from the size of the tank. This gives you the total length of Mollies that you can keep in your tank.
For Example
If the size of your tank is 50-gallon and the maximum size of the molly fish is 2 inches (balloon molly), now we calculate the number of mollies:
Number of Mollies= 50/2= 20
This means that the total inches of Mollies you can add in a 20-gallon tank are up to 19 inches (round off). Following the rule of thumb, we can add three female Mollies or two male Mollies. This will give us 18 inches of Mollies (3*4+2*3).
| Your Tank size (LxHxW) | Approx Volume* | Remarks |
| 24 x 12 x 12″ (61 x 30 x 30cm) | 10 gal (45 L) | up to 4 Mollies at most |
| 36 x 15 x 12″ (91 x 38 x 30cm) | 20 gal (89 L) | 6-8 Mollies |
| 36 x 18 x 15″ (91 x 46 x 38cm) | 30 gal (137 L) | up to 14 Mollies |
Can Molly Fish Live Alone?
No, molly fish cannot live alone as it is a social fish that flourishes in good company. We often think fish don’t feel anything and won’t get lonely if we leave them alone in the tank.
But we cannot get on the wrong side of loneliness than this. Imagine leaving an extrovert alone in a big room with no one to talk with. Can they survive? They might go on for a day or two, but they will crave human contact after that.
It is the same with your molly fish; they prefer to stay in a school with at least 6 of them together. Please do not make any decisions that will not work for you in the long run.
Maintaining Your Molly Tank
As essential as it is to keep the number of Mollies limited, we can not forget other important factors that we need to focus on to keep them in good shape and health. These little creatures swim freely in slow-paced but warm water sources like streams, pools, and coastal regions.
You should maintain a constant water temperature between 70°F and 82°F. It can range anywhere between these temperatures, considering the temperature requirements of other fish living in the tank.
It would help keep the temperature where all the inhabiting fish are comfortable living in. So whether you keep them in brackish fish tanks or freshwater aquariums, the pH level of water must be 7.5-8.5, whereas the hardness of the water ought to be around 15-30 dGH.
Maintaining Your Mollies’ Diet
As tiny as they are, you might have already guessed the diet of these little creatures. Known to eat more than they need to, you need to be careful not to overfeed your Mollies. They need to be fed 2-3 times a day.
You can feed these omnivores either live food or artificial food, even vegetables. They feed on plants, algae, and small invertebrates in their natural habitat.
Nonetheless, you can tear your kitchen vegetation, like lettuce, spinach, and zucchini, into small pieces and drop them in the aquarium. Then, you have the flexibility to combine them to have your DIY fish food.
As for live and frozen food, they prefer brine shrimps, bloodworms, and daphnia, whereas, for artificial food, the easy option would be pellets and flakes.
For healthy digestion of the Mollies, I suggest you only feed them the amount of food they can eat within about 3 minutes.
Decorations for your Mollies
I’ve repeatedly mentioned the accessories and decorations you can add to your aquarium. The extra additions assist in creating a better and more natural look-alike living environment for your fish.
For example, you can add sandy substrate, gravel, stones, and glass pebbles to add some color. You can also add live or artificial aquatic plants, rocks, corals, driftwood, etc.
These add essence and make your tank look more attractive, and the Mollies can use the plants and rocks as shades.
Does The Breeding Of Molly Matter When Choosing Tank Size?
Yes! While choosing the tank size, you need to decide if you want to breed your Mollies or not. They can produce 10-140 juveniles.
If you need 30-gallon of the aquarium for 14 Mollies, then we cannot even imagine the tank we would require for 100 of them. So unless it is for a commercial purpose, be careful when choosing the tank size.
Keep your eyes on them if you somehow plan to breed your Mollies or if they mate on their own.
Conclusion
From my experience, Mollies are a lovely species of pets. A little bit of attention to the number of Mollies you pet in your tank can give your eyes the pleasure of seeing these beautiful babies grow.
Overcrowding is a big NO. I hope that this article has been a guide to you for adding the Mollies to your tank. Irrespective of the tank size you own, a bigger tank doesn’t mean you add the Mollies in them thoughtlessly. It can be risky not only for them but also for your other fish.
Mollies need space to swim freely and remain healthy. I have loved being a keeper of the Mollies due to the ease of feeding and nurturing them. They are small and beautiful. Moreover, their peaceful nature makes it comfortable to be added with other tank mates.
If you want to add Mollies to your collection and learn more about them, you can read our article on Mollies at the given link.
Happy fish keeping!
Reference
Image Reference:
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