Guppies Tank Size: How Many Guppies are in a 5, 10, 20 Gallon Tank?

Guppy fish are lively, beautiful creatures and can bring any fish tank to life. But there might be something at odds with your particular fish tank. Do you think that there are too many guppy fish swimming around? Or maybe you feel a severe lack of these colorful vibrant fish. Whatever the case there might be one particular question that seems to swirl around your head.

This article aims to answer these questions and suggest how many guppies fish your tank can safely hold. Guppy fish do not hold back when making our tanks unmistakably beautiful so let’s give them the best conditions they deserve.

Generally, the rule of thumb when calculating space for any type of fish is a gallon for each inch of that fish. Meaning for every inch of space a fish takes up, a gallon of water will be required for them to meet its needs.

Guppy fish fall on the shorter spectrum when it comes to their size. Most adult guppies range around 1.5 to 2 inches and about 2 gallons for each guppy will be more than enough for them to be satisfied with their environment.

Like any other fish, guppies need their own set amount of space to swim around in but also shouldn’t find themselves facing trouble finding their way toward other fellow marine life.

Fish Tank

Tank Space for Young Guppies

But what if you happen to have a guppy under an inch in length? According to the previously advised rule of thumb: the amount of water needed for those guppies would be even less than a gallon right? Well, there are a few things to consider.

fish Space in the Tank

My advice would be to still consider sparing 2 gallons for those guppies. Since a guppy, you just bought can very well not be an adult yet. It would certainly create a problem as they begin to grow and proper space isn’t given in time.

Tank Space for Multiple Guppies

Guppies are social fish; they love the company of other guppy fish and being present within a community is vital to their stress levels and overall health which in turn affects their lifespan.

So instead of accounting for the tank space needed for just a single guppy, consider a tank that will be able to hold multiple guppies at once so that their needs as social animals are met.

Male-To-Female Ratio is Insufficient

It’s important to note that guppies do not need to be swimming along with other guppies at all times. Enough space should be given so that guppies have both choices of being by themselves or spending their time with other guppies.

What if there are Plants and Vegetation in your Tank?

Of course, it isn’t just the fish that take up space. Plants and vegetables bring a tank to life with their vibrant colors, and diverse structures directly correlating with the shades of the different fish that roam around your tank.

Plants and Vegetation in your Tank

As a matter of fact, being small and timid creatures, plants and vegetation along with any décor you put in are vital points of interest for all guppies alike. Guppies often use different plants and decorations as hiding places to hide from potential threats or aggressive tank mates. These hiding spots become crucial for female guppies when male guppies are known to hassle and stress out female guppies.

So if due for any reason your tank still happens to lack any form of vegetation; I would still recommend storing extra space for plants and rocks alike because they will definitely take up a copious amount of space.

What about the Future?

Plans and opinions change over time. It’s human nature to seek something new and at any point in the future, you may decide to expand the number of guppies in your tank. So if you do, browsing larger tanks to accommodate newly sheltered guppies will always be a neat idea.

What is the Ideal Guppy Tank Size?

Tanks come in all shapes and sizes, and so do fish. While different types of fish can provide different results, this portion of the article will focus on how many guppy fish can you store in different types of tanks.

Guppies Tank Size

You are free to adjust the number of guppies if you still feel your tank is making them uncomfortable to swim around in. To determine whether a guppy fish is swimming around normally, it should be able to swim for about 3 seconds or more before turning in the other direction.

So? How many fish should you consider? The following Tables should give a general idea of how many fish you can consider for your tank.

Small Sized Fish Tank

S.NoNumber of GallonsNumber of Fish
13 Gallons1 to 2 Guppies
26 Gallons3 Guppies
39 Gallons4 to 5 Guppies

Medium Sized Fish Tank

S.NoNumber of GallonsNumber of Fish
110 Gallons10 Guppies
225 Gallons12-14 Guppies
340 Gallons20 Guppies

Large Sized Fish Tank

S.NoNumber of GallonsNumber of Fish
145 Gallons22-24 Guppies
260 Gallons30 Guppies
375 Gallons36-38 Guppies

You may have noticed a pattern here. Most values for the number of fish are determined by using the formula of 2 gallons per guppy fish. So even if your own tank isn’t mentioned within these tables, you shouldn’t hesitate to use the formula to calculate the number for yourself.

How many Guppies are in a 5-Gallon Tank?

Continuing the pattern, we can safely store up to 3 guppies within a 5-gallon tank. They get plenty of room to breathe and swim around however don’t sit down just yet.

5-Gallon Tank

Taking care of a 5-gallon tank proves to be much more challenging than any bigger tank as water tends to be more stable in larger tanks. Therefore make sure you’re changing half of the water with fresh new water regularly and installing a filter can do nothing but help your tank stay healthy and clean.

How many Guppies are in a 10-Gallon Tank?

While 3 is still a minimum amount, you can take one step further and store up to 5 guppies in a 10-gallon tank.

10-Gallon Tank

What if you want even more? More guppies in a condensed area do give a pretty gorgeous effect, however, I don’t recommend putting their comfort at stake by throwing in more guppies. However, if you really want more guppies to swim around your tank I suggest installing an air pump beforehand. Always leave the air pump running and do not turn it off at night.

How many Guppies are in a 20-Gallon Tank?

Taking an even bigger leap – a 20-gallon tank gives way for you to store up to 12 guppies! The massive amount of guppies will look beautiful swimming around a 20-gallon tank but do consider the results of both genders being in the same tank. Guppies breed a lot and definitely take steps towards preventing more guppies from inhabiting your tank because the last thing we need in our tank is a spike in ammonia harming our guppies.

20-Gallon Aquarium

How many Guppies Should be kept together?

We’ve discussed plenty of where you should limit the number of guppies stored within a set amount of space. But is there a limit to the least amount of guppies you can store anywhere?

Well, the answer is pretty simple; at least three guppies are enough for them to stay calm and happy within their tank. This number happens to help us maintain a female-to-male ratio of 2:1 quite easily as well.

Keep a Higher Proportion of guppy fish Females Than Males

What if you want to keep only males in your tank? They are after all more bright and colorful, take less space than females, and wouldn’t make you worry about taking care of the unwanted fry.

I couldn’t recommend abstaining from that idea more as male guppies are very territorial and willing to fight other males for food and space; Inflicting wounds on other males which may eventually result in death.

Controlling the Population

Guppies like company; they’re social fish and can’t fathom the idea of themselves living a lonely life. But if you’re going to bring up multiple guppies within the same tank, how would you control them? In fact, a bigger question at stake is, how would you control their population?

1. Preparing for fry

I used to question what would I do about fry if a female guppy got pregnant. Would I get another tank for them? Should I expand the tank I already have to adjust for new fish? The answer is actually more straightforward than you might think.

Adult guppy fish often eat the fry when they’re birthed every month. This definitely eliminates the threat of more guppies to adjust to in a tank however you shouldn’t find yourself always relying on them alone.

Housing Guppy fry

Some adult guppies miss some fries and they end up growing as young guppies later on. If expanding the tank and adjusting for new guppies sound unpleasant to you and you simply want to maintain the number of guppies you have right now, then my advice would be to buy another tank to accommodate fry temporarily. Once they grow up, you can make the choice to either sell them, give them away, or return them to their original tank.

2. Keeping them in Groups

As mentioned plenty of times throughout this article, guppies are schooling fish; they prefer the company of other guppies to end up being alone.

 However, it is still possible to overdo it. Guppies don’t have to be swimming with others all the time. One of the only moments they always find themselves in a school is if they feel a sense of danger.

Keeping them in Groups

So sure, guppies like company but shouldn’t be always within range of other fish. But what would be the right number of guppies for one particular school? Normally 3 or more guppies are more than enough to keep them lively and active.

3. Different Territories for Groups

What if you want more than just a few guppies to roam around your tank? In this case, if your tank is big enough, different points of the tank can be used to occupy different schools. This way multiple schools can mark their territory on your tank and in addition your tank will create a diverse ecosystem where different groups of guppy fish spend their day in different pathways.

Factors to Consider while selecting a Tank for Guppies

1. Length of each Gender

Female guppies often tend to be larger in length, occupying more space than male guppies. Often taking up around 2 inches in length while male guppies grow up to be 1.5 inches. Of course, it can depend from guppy to guppy but I would still advise deploying 2 gallons for every guppy regardless of their gender.

2. The Behavior of each Gender

It may be tempting to choose more male guppies over females. They’re more colorful, and vibrant and give off an inviting tone for your fish tank. To end it all, they even take up less space. But I couldn’t stress enough how important a ratio of 3:1 female-to-male ratio is.

Guppy behavior

Male guppies are known to harass and stress out female guppies and adding more male guppies will not do them any favors regarding their comfort.

3. Overcrowding

This part of the article is pretty straightforward but I believe it is still pretty helpful to know how less space for each guppy can affect their mental health and stress levels.


If your tank becomes overcrowded, guppies being timid and fragile easily become stressed and worried. Spikes in ammonia are now abundant due to lack of space as well as aggression within different fish.

4. Keeping a Safe and Healthy Environment

While going out of your way to give your guppies the perfect amount of space will undoubtedly give in to a great effect – it will be pointless if the tank itself isn’t a safe and healthy environment. This last portion of the article is going to focus on a few tips where your guppy can swim free in the best condition and environment it deserves.

5. Keep Water Parameters Right

The ideal pH for guppies spans around 7.0 to 7.2 and the water’s hardness can range around 8 to 12 Dgh. Keep your guppies away from tap water as they contain plenty of harmful metals such as chlorine.

Set the fish Water Parameters Correctly

6. Tank Mates

Guppies may like company but there’s plenty of fish they watch out for as well. If your tank already includes fish other than guppies, then make sure they’re friendly towards smaller fish. If you’re looking for new fish to add to your tank, the few fish I would advise getting are:

  • Cardinal tetra
  • Kuhli Loach
  • Cory catfish

7. Filtering System

Filtering systems help remove ammonia and nitrites and keep the water hygienic and clean for fish of all nature. Never a bad idea to install a filtering system and keep your tank clean.

Peat Moss Filters

8. Temperature

The lifespans of guppies can be affected by the wrong temperature. A heater from a trustworthy supplier and a temperature from 72° to 82° Fahrenheit will do the trick in keeping your guppies comfortable.

Guppy Fish Minimum Water Temperature

The Bottom Line on Guppies Tank Size

So that was definitely a long ride for a pretty simple question. How many guppies can you keep in your tank?

To calculate for any fish, each inch of fish will equate to a gallon of water. The length of the fish shouldn’t be the only factor at play because the equipment, decoration, and plants will also end up taking up plenty of space.

Even when you determine the perfect amount of guppy fish for your tank, it is always a good idea to either keep a bigger tank or consider keeping fewer fish in case of fry or the unexpected growth of new guppies.

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