How Many Guppies in a 20 Gallon Tank? Avoid Overload With This Guide.

Estimated read time 6 min read

If you’re thinking about starting with a beginner fish tank, 20 gallons is the way to go.

And guppies are great fish to learn the ropes with. But the most important question to ask before you get started is how many guppies fit in a 20 gallon tank?

Guppies are considered low maintenance fish and are therefore enjoyed by many hobbyists, novice and professional alike.

However, just because they’re small doesn’t mean you can cram a bunch of them into one tank.

Guppies are schooling fish, so they do like to swim and hang out in groups. That means you should start with at least five.

Further Reading: Best freshwater aquarium fish

But different requirements may determine how many more you can have.

Keep reading for an in-depth guide to keeping guppies in a 20 gallon tank.


Some Equipment For Your 20 Gallon Guppy Tank

How Many Guppies Fit in a 20 Gallon Tank?

“How many fish can a 20 gallon tank hold?” is one of the most popular searches online for new fish keepers. And, the reality is that it depends on which type of fish you intend to keep.

For guppies, you should have no more than twenty, but that also depends on a couple of essential factors.


If you plan to keep all male guppies, you should have no problems housing twenty of them. Males are smaller than females. With that said, if you plan to have all females at an average of 2 inches each, you should only keep up to fifteen guppies.

If you want both males and females in your tank, it is recommended to have them at a ratio of 1:2, males to females.

Male guppies are more colorful, especially when they are trying to attract females. Because they are smaller, you should be able to fit at least four males and two females in your ten-gallon tank.


Pay close attention to their size, both when you buy the guppies and their full-grown size, as noted at the pet store. A twenty gallon tank can comfortably house fish load totaling up to twenty inches in length.

What If They Have Babies?

If you do keep males and females, there is a high chance you will end up with baby guppies.

You will not be able to keep the baby guppies in the same aquarium, so you should plan to either sell them, donate them to the pet store, or buy another aquarium. I like that last option, who doesn’t need another aquarium, Right!

Try separating the males and females into separate tanks to avoid more babies in the future.

Tank Maintenance Requirements

A 20 gallon guppy tank is pretty easy to take care of as long as you don’t have too many fish.

Make sure to keep the temperature between 72 and 80 degrees Fahrenheit and feed your guppies with a balanced diet.

Watch your filter for slow water flow, or for the media to turn green or brown, then you’ll know when it’s time to perform some filter maintenance.

Before you go, take a look at this post that talks about guppy care in more detail. Have fun!


Your filtration system is one of the most critical components in your routine fish care. A 20 gallon tank can require just as much filtration as a 30-gallon tank depending on the type of fish and environment you are trying to keep.

A good filter will include at least a 3-stage filtration system which consists of the following:

1. Biological Function

The waste produced by your fish, uneaten food, decaying plants will create ammonia. To sustain life in your aquarium, you must remove ammonia and your filters biological filtration provides a place for beneficial bacteria to grow, which in turn will turn your ammonia into nitrite and then nitrate as part of the nitrogen cycle.

2. Mechanical Function

Your filter floss or sponge is used to remove large particles and debris from your water. This helps to keep the water clean and clear.

3. Chemical Function

Water that you get from your tap, which most of us use for our aquariums will contain minerals, chemicals, and hard metals that can be bad for fish. Your chemical filtration, like carbon, will help remove some of these contaminants. Carbon can also help remove discoloration and odor from your tank.

Adding Live Plants to Your Aquarium

Guppies love grass and plant life to hide and play in. Besides that, plants add vibrancy and life to your otherwise dull aquarium. Too, plants can help improve your water quality by removing toxins produced by the fish, which also helps the plants to grow.

Look for flowing plants like duckweed, Amazon frogbit, and water lettuce. The following are some guppy favorites:

  • American waterweed
  • Guppy grass
  • Amazon sword
  • Java ferns
  • Wisteria
  • Hornworts
  • Watersprite


If you want happy fish for a 20 gallon tank, you should be sure to get them some substrate and even decorations.

The decorations for the tank do more than entertain you; they are private areas for the fish to hide, sleep, and claim their domains.

You can find various forms of substrates like gravel or sand. Gravel is the most common but more challenging to keep clean. You’ll need a siphon hose or water vacuum to use at least once per month.

Final Thoughts

How many male guppies can I put in a 20 gallon tank?

If you don’t want any babies, you can keep about 10 or 12 male guppies in a 20 gallon tank.

So that’s one guppy per 2 gallons of water.

If you plan on keeping males and females, it’s recommended to keep two females for every male or a ratio of 2:1.

Lucky guys!

In a 20 gallon tank, 12 would be the largest school you could keep. Keeping in mind, they will produce lots of babies.

How many guppies should be together?

Using the ratio of 2:1 (two females for every male), try to have schools in multiples of three, so, 3,6, 9, or 12.

That way, you can always provide the ideal ratio of male to female guppies.

Now that you know how many guppies fit in a 20 gallon tank, you can go ahead and get your aquarium ready.

Just keep these tips in mind for happy, healthy fish. Remember, don’t feed them too much, or you will end up with dirty, cloudy water.

We hope you found this guide useful and informative.

Learn More About Guppies:

How Many Guppies in a 20 Gallon Tank Avoid Overload With This Guide.

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