Best Tank Size for Guppies? (What To Look For When Picking)

Last Updated on 2023-05-24

Guppies are one of the most widely distributed fish in the world. Well-known for their colorful tails, guppies also happen to be incredibly easy to maintain. That’s exactly the reason why they make great pets. Keeping guppies happy requires a suitable tank, but most people aren’t sure what size to get. Scroll down to find out the best tank size for guppies and other relevant info you need to know if you are considering getting this fish. 

Whats the Minimum Tank Size for Guppies? 

Guppies don’t require large tanks because they’re not too large. That said, you still need to think about the size of the tank. Most people are led by the relatively small size of the fish and feel like “any” size of the tank is suitable.  

The industry standard for the minimum tank size for guppies is 5 gallons. However, it’s also possible to find recommendations that suggest the smallest tank size for guppies is 10 gallons. Although these fish are small, the goal is to make sure they are comfortable in a tank, so in a 10-gallon tank, you could hold around five fish.

Whats the Best Tank Size for Guppies? 

When choosing the best tank size for guppies, you need to take into consideration that you’ll probably hold more than a couple of them. Therefore, the tank should be spacious enough to provide all fish in a comfortable environment.

Generally speaking, you need one gallon of tank water for every one inch of guppy. An adult guppy is about two inches long on average, but some may reach the size of 2.5 inches. To simplify, the general rule of thumb is to add three guppies per 10 gallons of the fish tank. 

Although not a rule, most people hold guppies in groups. There is no set limit to how many guppies you can own or hold in a tank because multiple factors play the role. However, if you want to hold a larger group of guppies and you don’t mind spending money on a tank, then the best tank size for guppies would be 40 gallons.  

While it’s easy to think 40 gallons is too much, the tank of this size would allow you to hold many guppies without risking overcrowding. Plus, it’s also practical for those who aren’t sure how to determine the right size of the tank per length of each guppy.

It’s incredibly important to set up an environment where guppies will feel comfortable and be safe. You also need to bear in mind waste production, which would lead to the accumulation of toxins. That’s why the tank must have adequate size to prevent potential problems and complications.  

Moreover, getting a 40-gallon tank will also make it easier for you to place decorations and other accessories. They look much better in a bigger tank rather than in smaller counterparts.  

Speaking of tanks for guppies, it’s also useful to mention the temperature is important. Ideally, the temperature of water in the tank should be the same as in their natural habitat i.e., waters of Amazon and South America. Therefore, the ideal water temperature is between 72°F and 84°F (22°C to 28°C). 

How Many Guppies Can You Keep per Gallon? 

It’s always better to have a group of guppies in the tank mostly because they have company, but also provide a wonderful sight for us. Observing guppies and their vibrant colors can induce a calming effect and help us relieve stress almost instantly. Keep in mind that no fish tank is going to be full of water from top to bottom due to the additional equipment required for guppies. 

Some water volume is displaced when you add equipment such as air pump, water filter, and decorations such as substrate and live plants. As a result, the tank’s capacity is actually lower than you think. For instance, the 10-gallon tank won’t hold 10 gallons of water. 

As mentioned above, you need one gallon of tank water per one-inch of fish. So, a fish of two inches in length would need two gallons. If you have two male guppies that are 1.5 inches long and two females of 2 inches, then you may need a 7-gallon aquarium. 

If you’re not experienced in holding guppies and maintaining them, it’s smart to start with one or two first. A beginner should keep fewer guppies than someone with more experience. So, start small, and as you gain more experience, you may go on to get more guppies (and a bigger tank).  

Basically, the size of the guppies plays a role in how many of them you can hold in a tank. For example, if you’re looking for the optimal number of guppies in a 5-gallon tank, you need to do some calculations.

Based on the mathematical equation mentioned above, you can have five inches worth of guppies in a 5-gallon tank. This means that you could keep two females or three maximum. Additionally, you could keep three males in a 5-gallon tank or two males and one female guppy. That being said, keeping a male-female combination is not exactly recommended because they’re highly likely to breed. 

(Find out how many guppies you can keep in a 5 gallon, 10 gallon and 20 gallon tank.)

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What Happens If the Tank Is Too Small? 

Just because the fish are small, it doesn’t mean the tank size is irrelevant. Holding guppies in a tank that is too small can cause various problems, and some of them were mentioned above. Several guppies cramped in a small tank increase the waste production and accumulation of toxins. This can harm their health and lower their lifespan.  

That’s the last thing you want. You see, the nitrogen cycle is vital to keep the aquarium healthy. Fish produce waste, which then creates ammonia. Then, bacteria convert ammonia to nitrite, which then turns to nitrate in a normal cycle in the fish tank. But when too many guppies are grouped into the tank that’s not big enough, the whole cycle impairs and lowers the quality of water. 

Other problems can also occur. For instance, juvenile fish growing up in tank too small can experience stunted growth, atrophied muscles, spinal deformities, and other developmental products that jeopardize their health and function. All these problems decrease their lifespan. 

Besides health problems, putting too many guppies in insufficiently sized tanks can also cause problems among the fish. Just take a few moments to think about spending a lot of time with many other people in a small room. Eventually, they would get on your nerves and vice versa, right? The guppies (or other fish for that matter) aren’t that different.  

Multiple guppies in too small tanks lead to negative behaviors such as fighting for their space, aggression and increased temper. All these problems could have been avoided if the tank size is just right. 

Stress is yet another problem that guppies experience in a tank that’s not big enough to hold them. Just like in humans, the stress in fish can impair their body’s way to fight off diseases. Guppies in a suitable tank are more likely to fend off diseases due to favorable and pleasant environment. 

What Can Other Problems Apart from Tank Size Affect Guppies? 

Tank size is not the only factor that affects the health and wellbeing of guppies. Other factors also play a role and should not be overlooked. For example, the quality of water and filtration is crucial. After all, the quality of water directly influences the health of your guppies. Equipment you use in the fish tank can also contribute to deteriorating guppies’ health.  

The number of guppies and their gender is also important. As seen above, having too many guppies in a small tank can lead to several problems. Then, if you combine males and females, they may breed, which is not good (unless that’s exactly what you want).  

Other factors include: 

  • Temperature 
  • Salinity 
  • pH level 
  • Overfeeding and insufficient feeding  
  • Low oxygen levels 
  • Lack of hiding places 
  • Inadequate maintenance 


Guppies are popular fish thanks to their vibrant colors and beautiful tails. It’s perfectly reasonable why people want to get guppies; they’re easy to maintain and make us feel calmer. But a common mistake that many repeats are holding guppies in tanks that are not big enough for them.

While they are low-maintenance, these fish still need enough comfortable space to thrive. That’s why it’s crucial to get the tank with the right size. In this post, you learned more about the best tank size for guppies, but also the minimum tank size for these fish. Now that you know how many guppies you can keep per gallon, all you need is to bring these vibrant fish into your life. 

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