How Many Guppies in a 5 Gallon Tank? (Caution Advised)

Guppies are among my favorite fish to keep in an aquarium. They’re peaceful and require minimal upkeep, so they’re ideal for both novice and experienced fishkeepers. If you’re thinking about adding guppies to your 5-gallon tank, there are a few factors to consider.

So, in this article, you’ll learn how many guppies should be in a 5-gallon tank and how to calculate that number for future reference.  

Key Takeaways:

  • Optimal Number: The best number of guppies for a 5-gallon tank is 2 females and 1 male. This prevents overstocking and maintains water quality.
  • Breeding Alert: Be cautious of the rapid breeding rate of guppies. If you’re not prepared for a growing fish family, consider a larger tank or separate genders.
  • Beginner’s Note: If you’re new to fishkeeping, it’s advisable to start with a larger tank. Smaller tanks like a 5-gallon can be challenging to maintain.
  • Gender Matters: Male and female guppies differ in size and behavior. Males are more colorful but can be aggressive if kept together without females.
  • Water Quality: Due to the small volume, water parameters in a 5-gallon tank can change rapidly. Regular water changes and monitoring are essential.
  • Tank Maintenance: Invest in a good filter and heater to stabilize water conditions. Also, provide plenty of hiding spaces and live plants for your guppies.
  • Watch the Fry: Keep an eye on baby guppies (fry). They grow up fast and can quickly overstock your tank.

How Many Guppies in a 5 Gallon Tank? 

When it comes to keeping fish, a 5-gallon tank is the smallest size aquarium you should go for. The compact size of these fish tanks may make it seem it’s incredibly easy to stock them, but they can be quite tricky.

Because of the small amount of water in the tank, the parameters can change quickly and ammonia can build up a lot quicker. With that in mind, in my opinion:

You can keep 2 female guppies and 1 male guppy in a 5 gallon tank. Doing this will ensure that the males don’t harass females or attack each other. Any more guppies than this and your tank will be too overstocked which can cause the water quality to become poor.

One thing to be aware of is the level at which guppies breed, as it will overstock your tank very quickly. While it’s possible to keep guppies in a 5 gallon tank, 10 or more is definitely recommended.

And if your a beginner I’d also recommend getting a bigger tank even with just three guppies as it can be quite difficult to get the parameters perfect.

The reason for this is simple; as a beginner, you may not be able to handle the challenges that come with calculations of how many fish to fit in an aquarium and how to keep them healthy, maintain water quality, and more.

It’s always more practical to start with the minimum number and then move up. If you’re experienced at keeping guppies, then you may go for 5 of them, but it’s still a better idea to stick with 2 or 3. 

And, I can tell you from experience once more, if you’re keeping males and females together, they’re going to breed, so eventually you’ll need to get a bigger tank.

How Do You Calculate How Many Guppies You Can Keep in a 5 Gallon Tank? 

Always keep in mind that a 5-gallon fish tank is very limited, with the room for fish and decorations you can add. The good thing is that most 5-gallon aquariums come with a beginner’s kit, which features all equipment you need to set it up and maintain it properly. 

The calculation to how many guppies should be in a 5-gallon tank is not difficult. The general rule of thumb is one gallon per one inch of fish. Therefore, in a 5-gallon fish tank, you can add 5 inches worth of guppies. 2 female and 1 male guppy, just about hit this rule.

Since 5 gallons is very compact, you need to be careful when stocking tanks this small. Small aquarium calls for small fish (fortunately guppies check this box easily). That said, you can’t (and shouldn’t) try to stock as many guppies as you can.

This rule is important and applies to fish tanks of all sizes – you should never add too many guppies in the aquarium. What happens when too many guppies are present in a fish tank is going to be discussed further in this post.  

(Find out more about the male and female ratio.)

How Big Do Guppies Grow?

Guppies are quite small fish, and you can expect females to grow to around 2 inches in length. Males, on the other hand, tend to be a bit shorter, usually reaching about 1.5 inches in size. These little fish are known for their petite stature, which is one of the reasons they’re popular among aquarium enthusiasts. Their vibrant and diverse colors make them even more appealing.

Does Gender Matter? 

In some fish, differences between males and females are subtle and almost unnoticeable. Guppies are different, though. Male and female guppies have noticeable differences that confirm the gender, and this matters when deciding how many of them to add to your fish tank. The female body is bigger and rounder than the males.  

Males appear slim and longer. Additionally, male guppies are more colorful than females and are easy to spot with their vibrant colors, especially on tails. The reason why male guppies are more colorful is simple; they use their vivid color to attract a mate.

On the flip side, females tend to have silver or pale grey bodies. Even though female guppies can have some color, they’re still not as colorful as males. 

Besides the body “contour,” male and female guppies differ in size as well. Females can be twice as big as males. While males can grow up to 1.5 inches, females can reach 2 inches (or in some cases, 2.5 inches) in length. It is their size that makes the gender crucial. Two males have up to 3 inches in total, while two females have a combined 4 to 5 inches in length.  

Since they don’t occupy the same amount of space, it’s crucial to consider gender when calculating how many guppies to add to the 5-gallon aquarium.  

While you’re going to want to keep male guppies (as they’re more beautiful) if you only keep males in the tank then they’re going to be much more likely to fight.

When I first got into fishkeeping, I thought guppies were peaceful, and while they are too other fish, when I kept the males only together, they would chase each other around the tank until I added some females. So you should definitely plan on adding females too!

What Will Happen If You Add Too Many Guppies? 

Adding too many fish to the aquarium is one of the most common mistakes that people make. The mistake usually happens due to the lack of experience, but also because people get deceived by the small size of guppies.  

Here are some things that can happen when you add too many guppies to a tank.

Ammonia Spikes

Adding too many guppies in a fish tank can destabilize the water chemistry and cause the nitrogen cycle to stall. When this happens the ammonia in the tank will spike which will wreak havoc on your guppies health.

Even at low levels, ammonia can burn the gills of your guppy and cause ammonia poisoning. 


When your tank is overcrowded, aggression is going to occur as well. Especially if you’re keeping too many male guppies. They won’t have enough space to be alone, which will result in fin nipping.

As I previously mentioned, this was the biggest problem in my tank, until I added some females.

Not Enough Oxygen

In some cases, if the water isn’t getting oxygenated enough, then too many guppies can end up causing there to be a lack of oxygen in the tank. Which will result in a sudden and swift death for your guppies.

(If you’re still deciding what tank to get, here are THE BEST 5 gallon tanks on the market right now!)

Tips For Keeping Guppies In A 5 Gallon Tank

If you’re going to keep guppies in a 5 gallon tank, there are a few things you can do to ensure that you keep them as happy as possible!

Provide Plenty Of Hiding Spaces

First of all you should provide plenty of hiding spaces for them, so they can relax and rest. Any sort of store bought decoration, plants, rocks, or driftwood are going to be great for this!

Add Live Plants

On the subject of plants, these are also essential when you’re putting guppies in a 5 gallon tank too! Not only will they provide hiding places, they’ll also oxygenate the water as well as keep it clean.

Be Careful At Feeding Time

You should also be careful at feeding time! You don’t want to overfeed your guppies, but you also want to make sure that every guppy is getting fed enough. When you’re done feeding, just make sure that you remove any uneaten food after.

Change The Water Regularly

5 gallon is quite small, so make sure that you’re performing regular water changes. You should be changing the water in a tank this size around once a week, removing 10-20% of the water each time.

Invest In A Filter And Heater

Tanks this small are so susceptible to water parameters shifts. Even a strong draft or a particularly hot day can cause the conditions to fluctuate dramatically. So making sure you’re keeping a filter and heater in the tank is essential for your guppies survival.

Keep An Eye On The Fry

And lastly, you need to keep an eye on the fry in the tank as well. It will only take a couple of fry reaching maturity and before you know it your tank will be incredibly overstocked.


Here are some frequently asked questions that people have about keeping guppies in a 5 gallon tank.

How Many Male Guppies In A 5 Gallon Tank?

You can keep three to four male guppies in a 5 gallon tank, however, it’s not recommended due to the aggression that can occur. Ideally 6 or more male guppies is needed to reduce the chances of aggression, but this would overstock a 5 gallon tank.

How Many Female Guppies In A 5 Gallon Tank?

Because female guppies are larger, you’re only going to be able to keep two together. However, doing so can cause them to feel stressed as they’re shoaling fish that like to be in groups. The one benefit is that you won’t have to worry about breeding.

Can You Breed Guppies In A 5 Gallon Tank?

Guppies can and will breed in a 5 gallon fish tank, which would cause it to become overstocked extremely quickly. If you plan on letting them breed, you should have another fish tank ready or plenty of fish to feed the fry too.

The reason why you need to consider breeding is that it can lead to overcrowding. The general ratio is one male per two female guppies. Avoid having more males than females because it would intensify their breeding. If you’re not ready to take care of this problem, e.g., if you’re not experienced, then you should opt for a bigger fish tank.

How Many Guppies In A 10 Gallon Tank?

5-6 guppies will fit comfortably in a 10 gallon tank, as long as you’re sticking to a ratio of 1:2 males to females. However, at 10 gallons you could also consider other fish such as chili rasboras or ember tetras as well!

How Many Guppies in a 5 Gallon Tank_ (Caution Advised)


Now you know that if you plan on keeping guppies together in a 5 gallon tank, then the best choice is keeping 1 male guppy with 2 female guppies! While it is possible to keep 3 or 4 males together or 2 females together. Due to aggression or stress that might occur. It’s not worth it!

If you liked this article, make sure you check out the rest of the website. And if you’re curious, here’s how many guppies you can keep in a 10-gallon and 20-gallon tank!


About the author

Hey there! I'm Antonio, the passionate owner and chief editor of Betta Care Fish Guide. With over half a decade of hands-on experience, I've become your go-to expert for all things betta and tropical fish.

Over the past 5 years, I've not only kept bettas and other tropical fish but also connected with a diverse network of hobbyists, seasoned fishkeepers, and even veterinarians.

Now, I want to help other beginner fish keepers who had the same questions as me when they were just starting out! So they can save themselves a ton of time and keep their fish happy and healthy!