How Many Guppies Can You Keep in a 55-Gallon Tank?

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Are you wondering how many guppies you can keep in a 55-gallon tank? Then you have come to the right place to find an answer.

You can estimate how many guppies you will be able to keep in a tank by using a simple calculation that will let you know how many you can keep in a community tank.

The most commonly used calculation or estimation is that you can keep a guppy per 2 gallons of water.

That is only an estimation, of course, but it is the closest calculation that lets you know how many guppies can comfortably live together. Of course, you can cramp more of them together, provided that all other conditions are flawless.

The direct answer to the question:

In a 55-gallon tank you can keep about 27 adult guppies, if we strictly use the calculation we established earlier (1 guppy fish per 2 gallon of water volume).

But that can change, provided that you give them proper conditions to live in. If you go over this number, it might be hard to keep them in a tank, as they might not have enough space and might struggle. Let’s dive deeper into this topic.

How to Calculate the Number of Guppies for an Aquarium?

It is quite simple to do that. Every guppy fish has to have at least two gallons of water at their disposal to live comfortably. But there is more to this than simply calculating the number for the 55-gallon tank.

It is most probable that you won’t be able to fill the whole container with water, and that a few gallons of space will be lost, or a few gallons of water will not be filled.

That is because of the live plants you might have in the tank, the filter might take some space, the substrate will also take some of that space away. Also, there are other things like a heater and other gadgets that will reduce the space that you can use for the water.

Realistically, you can fill to up to 50 gallons of water at most in a 55-gallon tank. That means that the space for the guppies is reduced, and you should calculate this by the gallons of water and not by the gallons of the whole aquarium.

If you want them to be comfortable, then more than 25 guppies is probably not the best idea. Anywhere from 20 to 25 guppies for a 55-gallon tank is probably the most realistic number.

However, you can freely decrease the number to ensure that they are completely comfortable. It is better to have a few less than a few too much, because that can really cause many problems – from hygiene problems to overcrowding.

It can decrease the quality of life, and consequently, the life span of the fish.

As for the ratio of males and females, you should strive for a ratio of 2 females per a male. A 2:1 ratio allows the females to be more comfortable and prevents them from getting chased as much, and it allows you to control the population better.

If you do want to keep more guppies, there are some things that you can do to accommodate the larger numbers.

Is It Possible to Keep More Guppies in Your Tank?

It is possible to do so, but only under strict conditions, and if you don’t exceed that number by too much.

For example, you can add a few additional guppies (2-5), but you should first make sure that other things enable this. Here are some factors that enable you to have more fish in the tank.

Overfilter Your Tank

The significance of a good filter should never be downplayed. In fact, it is one of the most important things that you should consider before you set up the tank.

The best idea is to have a slightly more powerful filtration system in place, especially if you want to exceed the number that is recommended for your tank size.

If, for example, you want to have more than 25 guppies in a 55-gallon tank, then you should ensure a more powerful filtration system. But then again, you shouldn’t go overboard and put a too powerful system, which can potentially harm the fish.

But a slightly stronger filtration than normal would allow you to clean the water better, as the demands will definitely increase with the number of fish you have in the tank.

Use High-Quality Bio Media

This is an important aspect of filtration that you should take care of. A filtration system takes care of three stages of filtration – mechanical, chemical and biological.

Out of the three, biological is the one that is not usually noticeable quickly, but is just as important, if not even more important, than the other two filtrations.

The biological filtration takes care of the harmful ammonia and the nitrates that accumulate within the tank. And the more fish you will have, the larger the amount of the ammonia and the nitrates will be.

These are produced by the residue of the fish and accumulate overtime; they can sneak up as invisible harmful chemicals. Fortunately, a good bio media can take care of it and allow you to have more fish in the tank.

Use Lots of Live Plants

Plants are important, especially live plants. While they might get nipped at by the fish and consumed, they are most of the time more beneficial than the provisional plants that are often placed.

That is because they actually produce many beneficial chemicals like oxygen, and will get rid of the harmful ones like ammonia and nitrates. They can be used as a sort of a natural bio media.

Live plants are especially important if you have plenty of fish in the tank. The quality of the water can decrease at faster rates when there are more fish, and the live plants can help massively.

Aerate the Water

The plants can achieve this, but you will need a lot more oxygen once you have more fish in the tank. Aeration means exposing your water to air, which can bring more oxygen into the water.

That is an important component of the water, and can help with the water quality significantly. With aeration, you can remove many harmful chemicals and provide the water with more beneficial ones.

Chemicals like ammonia, heavy metals, carbon dioxide and others can be quite harmful for the fish, especially if in abundant quantities.

With aeration, you can easily solve this issue and provide more oxygen for the fish, which is an important chemical for survival.

Maintain Tank Regularly

The more fish you will have, the more maintenance you will have to do, which is self-explanatory. Don’t be lazy and do the maintenance, and the fish will be eternally grateful to you.

Clean the water and the tank regularly, do water checks and maintain the right water parameters, clean the substrate and the plants, and change the water from time to time.

You can do this once or twice a week, which will not take too much time, but can do a lot for the quality of life for the fish.


You can keep about 25 guppies in a 55-gallon tank, but you can keep even more of them under specific conditions.

Ultimately, it is up to you and your wishes, but always make sure that the fish are comfortable and have the proper conditions to thrive.

Updated: April 7, 2022
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