How Many Guppies in a 5 Gallon Tank?

Guppies are some of the best fish you can keep in the aquarium. Since they are peaceful and low maintenance, guppies are suitable for beginners, the same way they’re perfect for experienced people. 

If you have a 5-gallon tank where you want to add fish, guppies are always a good idea. Before you go ahead and buy guppies, it’s useful to learn a thing or two about the capacity and other factors that determine the number of these fish you can keep in the aquarium. Read on to learn how many guppies should be in a 5-gallon tank and get valuable input on how to calculate that number for future reference.  

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. These fish tanks get contaminated easily due to a small amount of water, so you will need to bear that in mind when deciding how many guppies in a 5-gallon tank to add.  

In a fish tank of this site, you can add 2 to 3 guppies. Beginners should opt for four guppies maximum. At this point, you’re just learning and navigating the maintenance of guppies and how fish tank works, so it’s not a good idea to go over the limit.  

The reason 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. 

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. 

 Since it is very compact, you need to be careful when stocking this fish tank. Small aquarium calls for small fish and 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.  

Before you even begin keeping guppies in the fish tank, you need to remember that it won’t be full of water from top to bottom due to equipment. To remain healthy, these peaceful and vibrant fish need enough room to move around. That’s why you need to follow the calculation, and you’ll be able to prevent problems that would arise by adding too many guppies into the aquarium. 

The calculation of 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. More precisely, you can keep three males in an aquarium of this size. When it comes to females, you may keep two, but experienced people can push for three.  

Some people may want to add both genders. Going by the formula mentioned above, you can keep two males and a female. Or, if you want to keep it simple, one male and one female guppy could be enough. Speaking of genders, the ideal ratio is one male per two females. The role of genders will be discussed further in the post. 

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

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 in a male guppy.  

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.  

Most people opt for males mostly due to their colorful look, but it’s also possible to add both genders; just make sure to take their length into account and always follow the formula of one gallon per one inch of fish. 

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.  

Their shortness might make it seem it’s perfectly okay to add as many guppies as you can to the aquarium, but the reality is different.  

The last thing you want is a formula to calculate how many guppies to add to the fish tank, but it’s necessary. The calculation is the best way to prevent problems that come with the overcrowded fish tank.  

Adding too many guppies in a fish tank can destabilize the water chemistry and cause the nitrogen cycle to stall. The nitrogen cycle is defined as the process of various bacteria converting harmful waste. As you can imagine, the process starts with waste expelled by guppies.

The decay of waste ends with the production of ammonia, which is toxic for guppies. Even at low levels, ammonia can burn the gills or impair oxygen supply. 

Your fish tank has a filter and other pieces of equipment that take care of this problem and make sure water is clean and oxygenated. That said, the filter’s function is not enough in the overcrowded aquarium because it is not created to work with that kind of capacity. This impairs the nitrogen cycle and lowers the quality of water, which can make fish sick.  

When you combine the poor quality of water and weak immune system caused by it, then you get a shorter lifespan of guppies. It’s also worth mentioning that young guppies can’t develop properly in an overcrowded fish tank. Developmental issues can also harm their lifespan and quality of life. 

Guppies are freshwater fish, meaning in their natural habitat, they swim in the current. Water in the fish tank shouldn’t be stagnant, and guppies should have enough room to swim, even in a small 5-gallon fish tank.

When you add too many guppies into the aquarium, there is a risk of frustration, stress, and even aggressiveness in these naturally peaceful fish, especially among males who may become territorial.  

What Effect Will Breeding Have? 

While you may be tempted to have both male and female guppies in the fish tank, you need to bear in mind these fish breeds. In fact, they breed a lot. One female guppy can have multiple pregnancies from one fertilization.

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 adding guppies of the same gender in one fish tank could be the safest idea for a start.  

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Minimum two and a maximum of five guppies can fit into a 5-gallon fish tank, but the latter is only recommended for experienced men and women. Now that you know how many guppies should be in a 5-gallon fish tank, you’re ready to start keeping these wonderful fish.  

And if you’re curious, here’s how many guppies you can keep in a 10-gallon and 20-gallon tank!

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