How Many Guppies In A Fish Tank? (1-75 Gallons)

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Quite often, I found myself wondering how many guppy fish can be placed in a fish tank. After a bit of research, I realized that the number of guppies depends on the number of gallons and objects featured inside. 

It is best to keep one guppy for every two gallons of water. For example, if you have a 10-gallon tank, you can have five guppies. If you have a 40-gallon tank, you can have 20 guppies, and so on. It is also recommended to keep 15% fewer guppies in overcrowded tanks to avoid conflicts.

As we move forward, I will provide you with the exact number of guppies you should put in your tank, depending on its size. Then, I will elaborate on the male-to-female ratio and show you how to adjust your tank for multiple guppies.

Also Read: 21 Facts About Guppies

How Many Guppies In A Tank? (1-75 Gallons)

If you intend to grow a school of guppies, here is a summary of how many you should put in a tank:

Small-Sized Fish Tanks:

  • 1-gallon tanks can hold one guppy.
  • 2-gallon tanks can hold one guppy.
  • 2.5-gallon tanks can hold one guppy.
  • 3-gallon tanks can hold 1 to 2 guppies.
  • 4-gallon tanks can hold two guppies.
  • 5-gallon tanks can hold 2 to 3 guppies.
  • 6-gallon tanks can hold three guppies.
  • 7-gallon tanks can hold 3 to 4 guppies.
  • 8-gallon tanks can hold four guppies.
  • 9-gallon tanks can hold 4 to 5 guppies.

Medium-Sized Fish Tanks:

  • 10-gallon tanks can hold five guppies.
  • 12-gallon tanks can hold six guppies.
  • 15-gallon tanks can hold 6 to 8 guppies.
  • 20-gallon tanks can hold ten guppies.
  • 25-gallon tanks can hold 12 to 14 guppies.
  • 30-gallon tanks can hold 15 guppies.
  • 35-gallon tanks can hold 16 to 18 guppies.
  • 36-gallon tanks can hold 18 guppies.
  • 40-gallon tanks can hold 20 guppies.

Large-Sized Fish Tanks:

  • 45-gallon tanks can hold 22 to 24 guppies.
  • 48-gallon tanks can hold 24 guppies.
  • 50-gallon tanks can hold 25 guppies.
  • 55-gallon tanks can hold 26 to 28 guppies.
  • 58-gallon tanks can hold 28 to 30 guppies.
  • 60-gallon tanks can hold 30 guppies.
  • 65-gallon tanks can hold 32 to 34 guppies.
  • 70-gallon tanks can hold 35 guppies.
  • 75-gallon tanks can hold 36 to 38 guppies.

As you can see, the number of guppies you can house in a fish tank depends on the size of the tank. Smaller tanks can hold one to two guppies, medium-sized tanks can handle five to six, and larger tanks usually accommodate a maximum of 30 to 40 guppies at one time.

Besides the tank’s volume, it is also essential to consider what it contains. For example, tanks that are overcrowded with plants and decorations can harbor many guppies that would not be able to find enough food.

Therefore, I suggest putting 15 to 20 percent fewer guppies in overcrowded tanks than what I recommended above. Also, when adding new guppies to an overcrowded tank, it is best to start with fewer guppies and gradually add more.

What About the Male-to-Female Ratio?

The ratio of male to female guppies should be 3:1. In other words, there should be three females for every male. Adding too many males will create unnecessary competition over females, ending up with conflicts and harassment. 

Also, adding more females will make breeding more likely to occur. But you should not add more females if you wish to avoid a high population of guppies. In this case, you can stick with one gender, either male or female.

How Many Guppies Should Be in a School?

There should be three to six guppies in a school. Growing fewer guppies than this will make the fish vulnerable to harassment by other species. On the other hand, having more than six guppies in a school will make it difficult for the fish to swim around and keep track of each other. 

Remember that schools are mainly for protection, so they do not have to swim together all the time. As long as they can stay close enough to each other when danger strikes, they can fulfill their purpose.

Tanks that are larger than 25 gallons may house multiple guppy schools. If you decide to keep multiple schools in a tank, one school can be housed at the top of the tank while another is housed at the base.

Can Three Male Guppies Live Together?

Three male guppies can hardly live together in the same tank. That is because male guppies are very territorial, and they will constantly compete for food. This will lead to fights between the three males. Instead, it is better to keep three females for each male.

This is an excellent practice to follow when you do not have enough space for three or more male guppies (20 gallons or more). If you really wish to keep only male guppies in a tank, it would be best if the tank is at least 40 gallons.

How Many Guppies Can Be Added at Once? 

When it comes to adding new fish to an existing tank, it is best to add one to two guppies at a time; do that in two day intervals. That way, the tank won’t get crowded and will still accommodate enough oxygen and food for the fish.

The most time-saving way to build a population of guppies is to add all the fish at once. However, adding too many guppies at once can overwhelm your tank and affect water quality. 

As a result, you will see drastic changes in fish behavior. For example, fish will stop eating or stop breeding. In other cases, they may cluster together and remain close to the bottom due to a lack of food and oxygen.

Can You Keep Just One or Two Guppies?

You can house just two guppies in a fish tank. Providing enough food for both of them will be sufficient for the time being. However, it is best to get at least three guppies within two months so they can help each other overcome adversity. 

Growing merely one guppy in the tank is generally not recommended. This is because guppies are social and prefer to live in schools. So the lone guppy might be unable to survive by itself, become stressed, and possibly die. However, if there are no other tankmates, one guppy can survive on its own.

How to Grow Multiple Guppies in a Fish Tank?

Picking the correct number of guppies doesn’t guarantee their survival. For guppies to thrive, they need the right environment and care:

1. The Right Water Parameters

The most important thing you can do to make sure your guppies are healthy is to maintain suitable water parameters. The most crucial ones are pH, ammonia, nitrates, and temperature. Then, you can check for additional factors, such as water hardness and chloramine.

Understanding the importance of pH is essential since it can affect your guppies’ health. A pH level in the 6.8–7.8 range is ideal for guppies.[1] When the pH is wrong, your fish may suffer from anemone loss and stunted growth, as well as a decrease in lifespan and fertility rates. 

Toxins such as ammonia, nitrites, and nitrates should be around 0 ppm. In the worst-case scenario, those elements shouldn’t exceed 0.5 ppm.[2] To measure the pH, ammonia, nitrites, and nitrates, I use the API Aquarium Test Kit (link to Amazon).

After testing dozens of kits, I can assure you that the API one is among the most accurate on the market. I personally use it at home whenever I’m doing a water change. It comes with everything you need to conduct a test, including a color chart. It’s super straightforward and easy to use.

The right temperature for guppies falls between 74 and 82 degrees F. It is also crucial that the temperature remains stable and doesn’t fluctuate. To achieve that, I use the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon).

I can say with confidence that this is the device you should get. Of course, it’s more expensive than the other devices, but it also outperforms them on all metrics: efficiency, longevity, ease of use, customer service, and many others.

2. Hiding Spots

If you are growing a school of guppy fish in your tank, it is vital to provide them with a few hiding spots. You can use plants like Java Fern or Anubias as well as decoration, such as a cave or an ornament.

I personally like Java Fern because it is one of the few plants that grow oxygen in aquarium water. It can also absorb nitrates from its environment. You can also use Moss Decorative Balls (link to Amazon) that provide more surface area for hiding spots.

A school of guppies that is exposed to other fish might suffer from harassment. Also, the guppies themselves might show hostility to each other, especially when it comes to males who are usually more territorial than females.

3. Picking the Right Tankmates

To successfully grow a school of guppies in a tank, it is also crucial to pick the proper tankmates. It would help if you stuck to fish like Mollies, Platies, Swordtails, and Cory Catfish.[3] These usually live in harmony with guppy schools.

On the other hand, avoid species like Angelfish, Bettas, Oscars, and Parrot Fish. These are relatively bigger than guppies and more aggressive so they can harm the guppies in your tank. If you don’t want to take any chances, you can start by growing only guppies.

4. Having Enough Oxygen

Growing multiple guppies in a fish tank can cause oxygen deficiency. That is especially true if you exceed the numbers mentioned in the earlier part of this article. Guppies that are suffocating will gasp for air at the surface, breathe rapidly, and in some cases lie at the bottom of the tank.

The best way to oxygenate a fish tank is to add an airstone. I personally use the Hygger Aquarium Air Stone Kit (link to Amazon). I chose this one because it comes with everything I need to make the oxygenation process easier: an air stone, tubing, and connectors.

All you have to do is fill up your tank with water and put the airstone at the bottom (preferably in the middle of the tank). The air stone will quietly oxygenate your tank, creating aeration and bubbles.

It is also essential to have enough surface area in your tank. As a rule of thumb, stick with aquariums that are wider rather than taller. This will allow oxygen to dissolve in your water and circulate around the tank.

5. Avoiding Overcrowded Conditions

Even if you pick the correct number of guppies, it is still recommended to avoid overcrowding. You can quickly go in that direction by adding other fish species or having too many plants or decorations. That will end up with ammonia spikes, stress, disease, and shortened lifespan.[4]

As a rule of thumb, your fish should be able to swim straight for two to three seconds without having to turn the other way. If that isn’t the situation in your tank, add 15 to 20 percent fewer guppies than what was mentioned initially.

6. Feeding Your Guppies Properly

When you grow a school of guppies, it is essential to feed them right. Overfeeding may end up with constipation, ammonia spikes, and acidic water. To avoid that, feed your guppies the amount they can finish within two to three minutes.[5]

Typically, fish should eat once a day. However, if you keep forgetting to feed your fish, I highly suggest considering an automatic feeder. In my tank, I use the Eheim Automatic Feeding Unit (link to Amazon). All you have to do is set the time, and you are good to go.

Also Read: Can Guppies Live In Saltwater?


This article contains tips that will help you successfully build a school of guppies in your aquarium. If you follow them, you should be able to implement this guide into your daily life for a long time. However, remember that this is a guide, not a set of rules. 

You should find what fits your situation best and build the right cluster of guppies in your fish tank. Then, to achieve the best results, use the tips mentioned above as guidelines, and add more guppies to your growing school when you feel comfortable with their numbers.