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How Big Do Guppies Get? | Guppy’s Length, Weight, and Height

How Big Do Guppies Get? | Guppy’s Length, Weight, and Height

Guppies are petite, modest fish with one of the biggest fan bases in the aquarium hobby. While many may attribute this popularity to their easygoing nature, appearance has always been at the forefront. In this blog, I’ll tell you everything about a guppy’s size. Let’s start with how big guppies get.

How Big Do Guppies Get?

Male guppies are usually 1.5-3.5 cm (1.6-1.4 in) long, while female is about 3-6 cm (1.2-2.4 in) long. Likewise, the average body weight for a male is 0.07 ± 0.1 g, while females weigh 0.13 ± 0.1 g. Lastly, the mean height clocks in at 9mm. 

An average guppy only lives for two years. Thus, guppies reach their full size quite quickly.

There are many varieties of strains produced by breeders through selective breeding, which are characterized by patterns, colors, shapes, and sizes. For instance, some guppies are known to have bigger fins and tails than others.

Thus, factors like these play a significant role in determining a guppy’s size.

The mystery of how big guppies get doesn’t end here. Let’s have an in-depth look at their sizes at various life stages.

How Big Do Guppy Fry Get?

At birth, guppy fry are about ¼ inches big. They learn how to swim right after being born and learn to hide soon afterward.

Since guppies eat their own babies, you need to ensure they’re safe from the very start as owners. You can use a divider and breeding tank to create a safe space for guppy fry.

Here’s an acrylic tank divider by Toyuto I love. It has been a lifesaver, literally.

toyuto Aquarium Fish Tank Acrylic Divider

How Big Do Juvenile Guppies Get?

Guppy fry enters the juvenile stage one month after being born. A juvenile guppy grows up to ¾ inches.

Naturally, the females will start to appear a bit bigger than male guppies.

By this point, you’ll also be able to tell a male from a female due to the stark difference in colors.

Juvenile male guppy
Juvenile male guppy

How Big Do Adult Guppies Get?

As we have answered above, an adult guppy is about 3-6 inches long for a female, while males are 1.5-3.5 inches long.

At about 6 months, guppies reach their peak maturity. If you don’t want them to reproduce, you’ll have to separate males from females.

However, around the end of their life, guppies lose their fertility levels drastically.

Why Have My Guppies Stopped Growing?

Sometimes, guppies may not grow to their full potential. It could be due to the wrong tank size and water parameters, insufficient diet, and even genetics. Many times, the reasons are merely rookie mistakes.

You need to dissect the causes behind stunted growth and take the necessary steps to prevent it.

A guppy tank
A guppy tank

Inadequate Or Too Much Aquarium Space 

Irrespective of what life stage they’re in, guppies love to swim actively throughout the day and even more in the developmental stage. If they’re not swimming enough, they’re only not getting enough exercise.

And lack of exercise has a detrimental impact on a guppy’s health and size.

On the other hand, too much tank space also backfires. Because of high water volume, fry and juvenile guppies have a more challenging time finding food. They will waste a lot of energy swimming around and foraging for food.

When you provide just the right amount of tank space, that energy will be channeled into growth.

Lack Of Water Changes 

Another tricky reason why your guppies aren’t growing is the faulty water parameter. Factors like off temperature, depleted oxygen levels, and spikes in harmful gas have severe negative impacts on a guppy’s health—ultimately hampering the growth process.

We can’t stress enough the importance of frequent water changes as they’re the most effective at getting rid of waste and toxins.

Lack Of Nutrition 

Guppies have a wide range of appetites and love a hearty meal. They need a well-rounded diet that should include both dried and live foods for adequate growth. Their diet should consist of a fair amount of calcium and phosphorus, along with traces of magnesium, sodium, and iodine.

Since guppies live in brackish water, they can absorb calcium and phosphorus through the gills. However, that won’t be enough.


Genetics plays a vital role in determining a guppy’s size. The size can be big or small, depending on the strain produced by breeders through selective breeding. In that case, irrespective of what you do, there’s not much you can do to move the needle.

Genetics doesn’t only influence size but also other unique traits like patterns, colors, and shapes.

So, if your guppy hasn’t reached the desirable size even after crossing the 6-months benchmark, you might want to discuss that with the seller.

Bent spine in guppies is one such genetic condition that stunts their development. If you want to read about it, here’s our quick guide.

How To Speed Up Guppy’s Growth?

There’s no magic formula to speed up a guppy or fry’s growth. For instance, you need to ensure a protein-rich diet, keep the fry separate, ensure proper water parameters, and offer ample space in the tank.

Several underlying factors collectively contribute to their growth.

Adequate Tank Space 

Ample tank space offers plenty of room for a guppy to forage, swim, court, and explore—promoting a healthy and happy lifestyle. In turn, this stimulates their growth relatively quickly.

The general rule of thumb is guppies need at least 2 gallons of water per, but they usually end up needing more. For a fry, half a gallon of water per fry should be enough.

A guppy tank is prone to the overpopulation problem, which is the main contributor to inadequate aquarium space. Other than that, if you have too many things going around in the tank, like unpruned plants or showpieces, it’s wise to get rid of them.

Feed A Balanced Diet

Nutritional deficiency stunts a guppy’s growth and fuels diseases and deformities by wrecking the immune system. Diet plays a significant role in guppy’s growth. Thus, it’s vital to fortify a guppy’s diet with growth-promoting nutrients like calcium and nutrients.

Guppy fry should be fed at least 4 times a day. You need to shift your focus to a protein-rich diet for accelerated growth, which is found in live foods like baby brine shrimp, eels, and micro worms.

Ensure Optimum Water Parameters 

Guppy fry grows notably well when the water parameters and optimum and stable. For this, you need to ensure that everything is favorable—from the tank’s pH level and temperature to oxygen level and hardiness.

Since guppy fry needs to be fed at least 4 times a day, the water is prone to get dirty real quick. Thus, you will need to perform water changes more often. If you don’t, nitrates and ammonia rapidly build up, and it won’t only stunt growth but also can be fatal.

I would recommend carrying out at least 3 smaller water changes of 15-20% every week.

Appropriate Artificial Light

Appropriate light doesn’t just help a guppy see well. It stimulates food intake by promoting better food conversion efficiency. Thus, guppies and guppy fry both need around 8 to 10 hours of light every day.

However, don’t get too carried away with the lights. Guppies are diurnal creatures that need to sleep at night.

If you expose them to excessive light sources, it will blur the difference between day and night for them—causing them to stress and stunt their growth.

Raise The Fry Separately

Guppies practice filial cannibalism, where they consume their own offspring. If you raise the fry and adult guppies together, you’ll soon be left with no fry. And if the fry are lucky enough to be alive, their growth will be seriously stunted by the fear for life.

Now there could be various reasons behind a guppy eating its own offspring. It could range from stress and overpopulation to replenishing their own fat storage. 

Separate Fry By Size 

Separating fry by size can seem cumbersome, but it’s indispensable. You need to separate fry by size and different age broods. Otherwise, the bigger ones will eat up all the food—leaving next to nothing for the smaller fry. And there’s no way your fry will grow speedily if they don’t get enough food. 

In general, bigger fry are also more agile and active than smaller ones. And there’s a good chance that the presence of larger counterparts will stress smaller fry—inevitably hampering their growth. 

Final Words: How Big Do Guppies Get 

How big guppies get is a relative question that depends on their genetic strain and various other factors. However, on average, a male guppy is about 1.5-3.5 cm long while females are 3-6 cm long. 

As for their average body weight, an average male guppy weighs 0.07 ± 0.1 g, while a female clocks in at 0.13 ± 0.1 g.

Guppies have been a separate species for several million years now. Thus, their anatomy has also changed drastically over time. Today, breeders produce several strains via selective breeding, which influences the size and patterns, colors, and shapes. 

Relevant Articles On Guppies:

Why is My Guppy Laying on Bottom of Tank? 8 Reasons Behind It.

What Fish Eat Guppies? Their Arch Enemies??

What is The Best Guppy Male to Female Ratio?