How Many Guppies Can Fit in a 10-Gallon Tank?




how many guppies in a 10 gallon tank

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Guppies are among the most famous freshwater aquarium fish, and their small size makes them a popular choice for nano tanks.

If you’ve got a 10-gallon tank, you may be wondering how many guppies you could keep in it. The answer is up to 5-6 guppies in a 10-gallon tank, but you need to be aware that guppies are livebearers and can multiply in numbers in numbers very quickly!

Managing a group of guppies in a 10-gallon tank requires a bit of understanding, so let us help.

Introducing the Famous Guppy

The guppy (Poecilia reticulata) is an icon of freshwater fish keeping. Their long, flowing tail fins, diverse colors, and intricate patterns have made them some of the most popular pet fish in aquariums worldwide.

Guppies are also the ideal beginner fishkeeper’s fish, being hardy, relatively peaceful, and even easy to breed.

Native to South America, they are members of the livebearing family, which makes them one of the few fish to give birth to live young rather than laying eggs.

Two Rules of Thumb for Stocking an Aquarium

Traditionally, fishkeepers have followed a simple formula to calculate the number of small fish they can keep per tank gallon. It goes like this:

1) Fish no longer than 3 inches long require one gallon of water per inch of body length. That means a 10-gallon fish tank can host up to 10 inches of combined fish body length.

An alternative method is to calculate the number of fish according to the surface area of the aquarium. Some argue this makes more sense since the surface area, rather than the tank’s total volume, is the most important factor in determining stocking density.

The surface area method goes like this:

2) Stock one inch of fish for every 12 square inches of aquarium surface water. A standard 10-gallon tank has a surface area of 128 square inches – which works out enough for 10.66 inches of combined fish body length.

Calculating the Number of Guppies for a 10-Gallon Tank

Common guppies are nano fish, with males growing to 1.5 inches and females reaching up to 2.5 inches long.

If we take the average guppy size to be 2 inches, then using the first formula, we’d only have space for five of them in an all-guppy tank of 10 gallons.

Using the second formula, a standard 10-gallon tank has enough room for 10.66 inches of small fish. This would mean space for just over five guppies, or six at a push.

Any more than five or six guppies in a 10-gallon tank would be considered overcrowding, which is a dangerous game.

The Dangers of Overcrowding

Overcrowding tanks is a common mistake made by beginners who are carried away by the inevitable excitement of owning their first tank.

It is also a strategy sometimes employed by experienced fishkeepers who want to make a dazzling impression with a tank that’s heaving with fish.

In reality, overstocked tanks are usually more fun to look at than to live inside, and they also require a lot more work to maintain healthy water conditions.

Tanks that are overstocked can get dangerously low in oxygen and high in toxic ammonia or nitrates. They can also suffer blooms of algae and water that quickly becomes cloudy.

To combat this, the fish keeper must constantly chase their tail to keep water parameters suitable for healthy fish and plant growth.

Fish that are stocked too densely will also become stressed and more prone to disease, and unless you want to be constantly changing your water and scrubbing your filters, we recommend you stay well away from overstocking your fish tank.

Male-Female Combinations of Guppies

As we mentioned, guppies are livebearers and are famously easy to breed. In fact, if you have both males and females, it’s very hard to stop them from breeding!

Since reproduction is such a high priority in the world of a guppy, you’ll need to think carefully about how you mix male and female fish.

Males can become quite competitive over mating with females and can even bully each other or fight if there are too many males in a small space.

Many guppy owners will tell you: the golden ratio for guppies is 1 male to every 2-3 females so that each of them will have enough females to keep them happy and out of trouble.

Remember that hosting males and females will always lead to reproduction. You need to think ahead about what you can do with the fry, or go for a single-sex group of guppies.

How Many Male and Female Guppies in a 10-Gallon Tank?

how many guppies in a 10 gallon tank

As we calculated, a 10-gallon tank is enough room for 5-6 guppies. If we want to follow the golden ratio of 1 male to every 2-3 females, then a 10-gallon would give us enough space for four females and a maximum of two males.

Males are often considered especially desirable because of their brighter colors and fancier fins, so it’d be understandable to want to keep more than one. So for a mixed group of guppies in a 10-gallon tank, two males and four females would make a fine choice.

Breeding Guppies in a 10-Gallon Tank

A pregnant female guppy can give birth to between 1 and 200 fries, so you can imagine how quickly their numbers could escalate. Luckily, the first time is usually less prolific, so if you’re new to guppy keeping, you’re unlikely to be overwhelmed with 200 new tankmates overnight!

But still, in a fully stocked aquarium, you need to think about what to do with the extra fish.

Setting Up an Additional Breeding Tank

Setting up a separate tank for breeding is a good option if you’d like to raise the guppy fry to adulthood. Since adult guppies like cannibalizing baby guppies, it’s safer to rear them in their own tank. This additional tank should be at least 10 gallons and have a sponge filter and heater to maintain gentle, stable conditions for the young guppies to grow up in.

In this case, the pregnant female is placed in the breeding tank before giving birth (either in a breeding box or free-swimming) and removed from the aquarium as soon as birthing has finished. The newborn guppies are allowed to grow up in a safe environment until they’re big enough to live with adult guppies or other community fish.

Birthing in the Parent’s Tank

If, on the other hand, you only have one 10-gallon tank that already has six guppies, you won’t have space to accommodate any more safely. You’ll either need to catch the fry a few days after they’re born in a net and offer them to a friend or pet store who can raise them or let the adults eat them.

The latter option can be rather disturbing to watch from our human perspective. Nobody knows exactly why guppies eat their young, but there will likely be a few survivors anyway that you’ll still need to deal with.

The prospect of guppies breeding isn’t so simple if you’ve only got one 10-gallon tank – which is why some fishkeepers prefer to keep guppies in single-sex groups.

Keeping an All-Male Group of Guppies

Keeping only male guppies is one way to overcome the over-breeding problem. Males are more brightly colored with fancier fins, so all-male groups of guppies are understandably popular.

But all-male groups of guppies, sometimes known as guppy fraternities, aren’t without their problems either! Their relentless search for a female to mate with could make them stressed and frustrated and cause them to possibly take it out on one another.

All-male groups of guppies in a small tank can sometimes become aggressive towards each other, and injured fish with nipped tails can quickly lead to fin rot and other diseases that are much better avoided.

Keeping an All-Female Group of Guppies

Another way of resolving the breeding dilemma is to keep an all-female group of guppies.

This is a less popular option owing to the more subdued colors of the girls, but female guppies can still have some nice patterns and beautiful fins.

An all-female group of guppies can still raise some territorial behavior and aggression between individuals, but normally much less so than among males.

Reducing Aggression Among Guppies

As we’ve said, guppies are relatively peaceful fish, but territorial disputes and frustrations around breeding can still lead to some unsavory exchanges, especially in a small tank.

If you’re keeping only male guppies, you must be especially careful to provide a tank that reduces aggressive behavior.

You can curb aggression among your guppies by providing them with plenty of hiding spaces. Guppies enjoy swimming among aquatic plants, which will also help them retreat from aggressive conflicts.

The ultimate solution to aggression, though, is a larger tank with a lower stocking density. In a 20-gallon tank stocked with other peaceful fish species, conflicts are much less likely to become a problem.

Whatever You Do, Breeding Mistakes Can Still Happen!

Whether you’re looking to keep an all-male or all-female group of guppies, you must also know that it’s quite hard to distinguish the gender of guppies when they’re young.

Female guppies can sometimes get pregnant in the shop before buying them!

All of this means that there are no guarantees you won’t have some baby guppies on your hands, despite your intentions! It’s good to be prepared for all scenarios.

Can You Keep Other Fish or Invertebrates With Guppies in a 10-Gallon Tank?

You could keep some other smaller fish, shrimp, or snails alongside your guppies in a ten-gallon tank, but it’ll mean less space for your guppies.

Since guppies should be kept in groups of at least three, you’ll need to seek out other species that will be happy in the remaining 5-gallons of water.

Other schooling fish is not a good idea because you won’t be able to stock enough of them to allow them to feel safe in their group.

Sparkling gouramis, Gold Spotted-plecos, Amano shrimps, and Cherry shrimps would all make suitable tankmates and will bring extra interest and diversity to your tank.

Snail species such as Nerite snails and Mystery snails are beautiful in their own right and will also help to keep your tank clean.

Some people have also tried keeping betta fish, aka. Siamese fighting fish alongside their guppies, but this can be a risky business in such a small tank. The guppy’s long fins and ability to eat food faster than a betta might trigger your betta’s fighting instincts, which could end up badly for your guppies!

To keep bettas and guppies together, a 15-gallon tank or 20-gallon tank is a much better option.

Can You Keep Guppies in a 5-Gallon Tank?

Yes. But 5 gallons is the minimum tank size you should ever keep guppies in. Being half the size of a 10-gallon tank, you could keep three guppies in 5 gallons of water.

Of course, the breeding dilemma is even more pronounced in a smaller tank, and 5-gallon aquariums are notoriously difficult to maintain stable water parameters.

Since 5 gallons is the very minimum space you should keep guppies in, you might want to consider going for the smallest types of guppy you can find. The Dwarf Panda guppy and Ginga Rubra guppy are two kinds of true guppy that have been bred to be smaller than most.

Another option is Endler’s guppy or Endler’s Livebearer (Poecilia wingei) – a species of livebearer that is closely related but smaller than the common guppy. While Endlers are very beautiful, do note that they can hybridize with common guppies – so mixing the species together is not a good idea!


Five or six guppies can be suitable for a 10-gallon tank, but it’s really important to consider their ability to breed and multiply in numbers quickly.

An overstocked tank can be dangerous for the fish and stressful for you to manage.

All-male or all-female groups of guppies might be a better choice in such a small tank, or you could consider looking at a 20-gallon aquarium which will be far more forgiving in terms of the space it offers extra fish, as well as being easier to maintain stable water conditions.

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