How Many Mollies in a 20 Gallon Tank: A Complete Guide




How Many Mollies in a 20 Gallon Tank

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One of the mollies’ priorities is having plenty of space to swim around and stay active. Therefore, you should think twice about how many mollies you want in your 20-gallon tank. So, How many molly fish can live in a 20-gallon tank?

The general guideline is to keep one inch of molly per gallon of water. Based on that, you could conceivably house five or six mollies in a 20-gallon tank.

In this article, I’ll dive deeper into how many mollies you can keep in a 20-gallon tank and offer tips on stocking your aquarium safely and responsibly.

How Many Molly Fish Can I Keep in a 20-Gallon Tank?

You can keep 5 to 6 molly fish in a 20-gallon tank. These friendly fish reach a maximum size of around 3 inches, so they’re not the biggest fish in the world.

However, they are very active swimmers and need plenty of room to move around. The one-gallon-per-molly inch rule of thumb is a good starting point when stocking your aquarium.

Of course, there are a few other factors to consider when deciding how many mollies to keep in your 20-gallon tank.

For example, if you’re planning on keeping other fish in the tank with your mollies, you’ll need to adjust the stocking density accordingly.

Another thing to think about is that this rule doesn’t apply to rocks, plants, and other decorations you put in the fish tank. Furthermore, it does not consider the fish’s height or that some fish grow longer or taller than others. Even though it’s a helpful guide, it isn’t perfect!

How Many Female and Male Molly Fish To Add in a 20 Gallon Tank?

You can accommodate up to 4 female mollies and 2 males in a 20-gallon tank. This way, every male will have two females to mate with, and there won’t be too much aggression between the fish.

This is because the male attention will be divided between the females, and there will be more room for everyone to swim around without feeling cramped.

Of course, you can keep all female or all male mollies in your aquarium if you prefer. Just keep in mind that a group of all males may fight with each other for dominance, while a group of all females will have a great time schooling together.

Overall, don’t forget to add some vegetation and other hiding places to give your female mollies a break from the males when needed!

How Many Black Mollis To Add in a 20 Gallon Aquarium?

A 20-gallon tank can accommodate 3-4 black mollies. For a single male black molly fish, you need to keep 3 female black mollies only to reduce the aggression.

If you want to keep more than one male black molly, you should also increase the number of female mollies. The ideal ratio of males to females is 1:3. So for two male black mollies, you should have six female black mollies in the tank.

However, this would be a close stocking ratio, and you might end up with oxygen-deprived mollies. Therefore, a 30-gallon tank size for housing mollies.

How Many Dalmation Molly Fish Can Live in a 20 Gallon Tank?

You can only keep four dalmatian mollies in a 20-gallon tank. These popular fish are usually big compared to other species and can grow up to 4.75 inches.

If you want to turn your tank into a breeding ground, you should only have one male and three female dalmatian mollies.

The ratio of male to female dalmatian mollies should be 1:3 because the males are very aggressive mollies in mating. If you have more than one male in the tank, they will fight each other for dominance.

And lastly, don’t forget that you need to provide hiding spots in the tank for the female mollies because the males will continuously try to mate with them, which can be very tiring!

How Many Ballon Molly Fish Can Live in a 20 Gallon Tank?

6 to 8 balloon mollies can stay in a 20-gallon tank compared to other molly fishes because this breed is relatively small.

Although balloon mollies are naturally peaceful, you still need to be careful about the stocking density. If the tank is too crowded, it can lead to aggression and fighting among the fish.

How Many Guppies To Keep With Mollies in a 20 Gallon Tank?

In a 20-gallon tank, you can keep up to 8 – 10 guppies with mollies. Guppies are generally quiet, like mollies, so they make good tank mates.

At a bare minimum, you can keep 8 guppies with 3 mollies. However, depending on specific larger molly breeds, this number may differ.

How Many Platies To House With Molly Fish in a 20 Gallon Tank?

You can house 10-12 platies with mollies in a 20-gallon tank because they don’t require much space. In fact, compared to mollies, they need almost half the amount of space. Therefore, many platies can coexist peacefully with one molly fish.

Keep in mind that platies are very active fish and need a lot of space to swim around. So, don’t overcrowd the tank with too many fish!

How Many Tetras To House With Molly Fish in a 20 Gallon Tank?

You can keep 6 – 8 tetras with mollies in a 20-gallon tank. To house mollies and tetras together, ensure that the tank has plenty of hiding spots and plants.

If you want to keep glowlight tetras, a maximum of 6 can live in a 20-gallon tank with 3 – 5 mollies. However, when I kept my mollies with 6 glowlight tetras, I noticed that the tetras were quite nippy and constantly harassed the mollies.

So, I tried adding some more plants to the tank, which seemed to help a little bit. I could see them swimming around and minding their own business after that.

Thus, when stocking a 20-gallon tank with mollies and tetras, watch them closely for the first few days and see how they interact with each other. If everything seems fine, then you can leave them be. But, if the tetras are too nippy, try to stimulate their environment a bit more.

What Fish Can I Keep With Mollies in a 20-Gallon Aquarium?

Cichlids are the ideal fish tankmates for mollies. They get along with mollies and don’t harass them like other fish species.

How Many Mollies in a 20 Gallon Tank

But while choosing the fish tank mate for your mollies, make sure they are not too big or too small. If they are too big, they might eat your mollies; if they are too small, the mollies might eat them!

Some good cichlid choices for a 20-gallon tank are:

Last Words

Mollies are a great addition to any aquarium and make for entertaining fish to watch. They are active, social creatures that enjoy the company of their own kind and other tank mates.

While a 20-gallon tank is suitable for housing mollies, overcrowding can cause many problems, including the risk of fish mortality, behavioral issues, stress, growth issues, and oxygen level issues.

I hope this article was helpful and that you now better understand how many mollies can live in a 20-gallon tank. If you have any further questions, please don’t hesitate to ask in the comments below. Thanks for reading!

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