Best Tank Size for Keeping Guppies

How Many Molly Fish In a Tank?

If you have recently decided that you want to add a molly fish to your aquarium, you are probably wondering how many molly fish you can have per gallon.

To cut the long story short, molly fish needs at least a 10-gallon aquarium.

This tank size can accommodate a small group of mollies, about 3-4 fish. If you want a bigger group, you will need a larger aquarium.

This guide will give you more details on how many molly fish per gallon you can have in your aquarium and how to calculate the stocking density for your beautiful fish.

How to Calculate the Number of Mollies That Will Fit in Your Tank?

As a general rule of thumb, you can calculate the number of molly fish your tank can accommodate by using two factors, the tank size and the max length of molly fish.

The secret to figuring this out is “Size of the tank ÷ Max Length Of a Molly Fish = Number of Mollies.”

For example, if you have a 50-gallon aquarium, and the max length of your molly is 3 inches, then 50 ÷ 3 = 16.6.

This means you can have approximately 17 Mollies in your tank.

However, for optimal calculations, you must consider the other factors while stocking your tank. Decorations, plants, and other objects in the tank will also occupy some space.

Therefore, you should calculate the stocking density by considering the decorations and other objects.

For example, if you have a 50-gallon aquarium and you want to put some ornaments and plants in it, then the stocking density would be

50 – (Number of Ornaments + Number of Plants) ÷ Max Length Of a Molly Fish = Number of Mollies.

This means if you have a 50-gallon tank and want to put 5 ornaments and 10 plants in it, the stocking density would be 50 – (5 + 10) ÷ 3 = 11.6

This means you can have approximately 12 Mollies in your tank.

What Is the Best Tank Size for Molly Fish?

You can keep most molly fish in a tank of as little as 10 gallons. 

Depending on the calculations we did in the previous section, this tank size is suitable for 3 to 4 mollies. So, it wouldn’t help to take it for granted and stock as many mollies as possible in such a small tank.

If you want to add more mollies, which is preferable because mollies are social creatures and love to be housed in groups, you need to increase the tank size. The larger the tank, the better.

How Many Molly Fish In A 5-gallon Aquarium?

It’s better to keep only one molly in a 5-gallon tank. However, from my expertise and understanding, I urge you not to keep your molly alone.

How Many Molly Fish In A 10-gallon Aquarium?

You can only keep a maximum of three Mollies in a 10-gallon aquarium. You can only keep a maximum of three Mollies in a 10-gallon aquarium. However, if you have a tank without any decorations, you may be able to stock 4 mollies.

How Many Molly Fish In A 20-gallon Aquarium?

You can stock up to 6 Mollies of 3 inches in a 20-gallon aquarium. However, if you have any decorations or other objects that occupy space in your aquarium, then 4-5 mollies would be perfect.

How Many Molly Fish In A 30-gallon Aquarium?

10 Mollies is the stocking density for a 30-gallon aquarium with no other objects taking up space. This number may change if you have other objects in your aquarium.

Can Molly Fish Live Alone?

Mollies are shoaling fish, not schooling fish. They enjoy having company, but they can survive alone if need be.

However, it’s not the ideal situation for a molly fish. In the wild, mollies live in groups of 20 or more. So, if you’re keeping mollies, it’s best to have at least six of them.

Does the Breeding of Molly Matter When Choosing Tank Size?

Yes. If you want to breed Molly fish, you must take the tank size into account.

You need about 10 gallons tank to house just 3-4 mollies, let alone if you have 30- 40 or even a hundred.

I know that fry mollies are tiny and don’t occupy much space when they are too young, but you’ll see how space matters as they grow older.

As a rule of thumb, you can start with a 20-gallon tank. By the time your fry mollies have grown to adult size, you may need a 55-gallon tank or even larger, depending on how many mollies you have. 

8 Things to Manage While Keeping Molly Fish Together

1. Water Temperature

Molly fish are tropical fish, and they prefer warm water. The appropriate water temperature is between 70-82 Fahrenheit.

The water should not be too cold or too hot for the fish to survive. Otherwise, the fish can get stressed, which can lead to diseases.

2. pH Level

Molly fish are sensitive to changes in water conditions, especially the pH level. The ideal pH level for mollies is between 7.5-8.5.

If the pH level is too high or too low, it can cause problems such as gill damage, skin irritation, and stress.

3. Water Hardness

Maintaining the right water hardness is important to keeping molly fish healthy. The hardness of the water should be between 5 and 30 dGH.

4. Water Quality

The water quality is of utmost importance because it keeps the fish healthy and suitable for living. The ammonia, nitrites, and nitrates should not exceed zero ppm.

Therefore, regular water changes are necessary to ensure that your tank’s water quality is up to par. We suggest a 20-25% water change every 2-4 weeks.

5. Filtration System

Filtration is an important process in any fish tank because it helps remove toxins and bacteria from the water, making it safer for your fish to live in.

Many different types of filters are available on the market, so be sure to do your research and choose the one that is best for your tank.

6. Lighting System

Proper lighting is essential for the growth and well-being of your molly fish. It also helps to show off their beautiful colors.

Be sure to choose a light specifically designed for aquariums, as regular household lights can harm your fish.

7. Tank Decorations

When choosing decorations for your tank, be sure to pick ones that are safe for your fish and will not tear their fins. Some good options include live plants, driftwood, or rocks.

These decorations will help make your tank more aesthetically pleasing and provide your fish with hiding places.

8. Balanced Diet

Mollies are omnivores that feed on tiny invertebrates, algae, and plant debris in the wild.

To satisfy their needing in your aquarium, you should feed them high-quality flake food and a range of fresh vegetables.

They enjoy zucchini medallions, cucumber medallions, and shelled peas. If you don’t have the time to process vegetables, or spirulina is not an option, a flake or pellet made from spirulina can suffice.

Last Words

Molly fish are great additions to any aquarium. They are beautiful, hardy, and easy to care for.

When choosing a tank size for your Mollies, be sure to consider the number of fish you want to keep and the water parameters and decorations in the tank.

We hope this article has been helpful and informative. Thanks for reading! If you have any questions or comments, please feel free to leave them belo

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