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How Long Does It Take For Baby Guppies to Grow? Our Vet Answers (With Pictures)

Dr. Luqman Javed, DVM (Vet)

By Dr. Luqman Javed, DVM (Vet)

Multi color Poecilia reticulata,on nature background with clipping path

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Dr. Luqman Javed

DVM (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Did you just get your hands on some guppy babies, also known as fry? Or maybe you already have guppies and they just decided to breed. You might be wondering how long it takes for guppies to grow and how big they will get.

Generally speaking, assuming proper water conditions, an appropriate diet, and excellent genetics, guppies take around 3 months to reach sexual maturity and around 6 months to attain their adult size.




Guppy Fish Size, Growth Rate, & Growth Stages

Guppies usually attain an adult size of around 1.5 – 2 inches. However, like all fish, several factors can influence their ability to grow to their genetic potential. Strictly speaking, fish never stop growing until they die, so even an adult fish continues to slowly grow all the time (albeit slowly). This makes fish and other cold blooded animals somewhat different from their warm blooded counterparts.

Nonetheless, it’s safe to say that most healthy guppies that receive appropriate care attain sexual maturity at around 3 months of age, and reach their “adult” size at around 6 months of age.

Their growth isn’t linear, which means that they don’t grow at the same pace on a weekly or monthly basis. Like many other animals, they have a growth spurt of sorts when they’re young, and during this developmental period, they grow rapidly in size – assuming their needs for proper growth and development are met.

The 4 Growth Stages

1. Birth

guppy fish baby
Image Credit: livingpitty, Shutterstock

Guppies are livebearers, which means that they give birth to live fish, not to eggs. The guppy fry is born at roughly ¼ inch in length.

They look a little deformed for the first few hours but will quickly gain their natural shape, and they start swimming as soon as they are born.

2. Juvenile

Full red guppies
Image Credit: Mircea Costina, Shutterstock

A guppy is considered a juvenile when they’re not able to reproduce sexually, but are large enough to not be eaten by the adults and can swim alongside them. This usually happens when they reach a size of around an inch or so. The timeline for this is around 1-2 months. There is a great deal of variance because external factors can influence the rate of a guppy’s growth. We’ll dive into these factors shortly.

3. Young Guppy

little baby guppy fish
Image Credit: Magdalena Teterdynko, Shutterstock

The next 4 months of the guppy’s life is the young guppy stage. This is when guppies should be sexually mature, and this is where the rest of their growth will occur, from ¾ inches to 2 inches in length.

4. Adult Guppy

Motley guppy Poecilia reticulata male in aquarium
Image Credit: Miroslav Hlavko, Shutterstock

Guppies are considered adults when they’re 6 months old. You can expect a guppy to live for about 2 years on average.


What Factors Influence a Guppy’s Growth?

Several factors influence a guppy’s growth rate:
  • Genetics: larger and older female guppies tend to have fry that can attain a larger size on average.
  • Nutrition: all fish need nutrition to grow properly. Guppies are no exception to this rule
  • Aeration: guppies need well oxygenated water to grow properly.
  • Space: the amount of free swimming space your fish have will determine their growth rate. In large aquariums, the fry may burn more calories chasing food that’s offered to them and grow slower than in an appropriately sized aquarium. However, a smaller space requires better filtration and careful maintenance.



How Often Do Guppies Have Babies?

What is pretty insane about guppies, especially the females, is that they can give birth to a whole lot of live fry at once, and they can give birth very often too.

Under the right aquarium and breeding conditions, a female guppy can give birth to a new batch of fry every 30 days, and each time she does, she can give birth to between 20 and 50 guppy fry.

So, if you have males and females in your tank, you can expect new guppy fry to appear roughly once per month.

Image Credit:Toxotes-Hun-Gabor-Horvath, Shutterstock

Do Guppies Eat Their Own Babies?

Yes, the adults indiscriminately eat any fry they can fit in their mouths, and therefore, female guppies should be separated from their tank mates when they’re about to give birth. Alternatively, the aquarium should be densely planted with moss to provide the fry cover. However, this doesn’t guarantee their survival.

guppy fish in aquarium
Image Credit: Piqsels

Do Guppies Die After Giving Birth?

No, this is a myth and it is not true. Guppies do not die after giving birth. Once a female guppy is sexually mature, she can give birth roughly every 30 days on average, assuming conditions are correct. However, other factors (such as parasitic diseases) can obviously lead to the demise of a female guppy if left unaddressed.

Female Guppy
Image Credit: hadot 760, Shutterstock

General Guppy Breeding Tips

Guppies are very easy to breed, and generally speaking, you don’t necessarily have to try to breed them. If a female guppy has spent a day with a male, odds are she’s mated with him. What’s more, is that a single mating session allows a female to hold enough sperm to impregnate herself three times (females can store sperm for use later on). This means that a female can spend around 3 months away from a male after spending a day with him.

Guppies do not lay eggs, and all a female needs when she’s about to give birth is a secluded area (in a breeding trap or a separate aquarium). Once she’s birthed her fry, she will look visibly thinner in her abdomen, and she should be separated from her fry. Female guppies have no maternal instinct and will eat their fry if the opportunity arises. The fry are fully self sufficient and able to feed themselves from birth.



When properly cared for, guppies take around 3 months to attain sexual maturity, and 6 months to attain their general adult size. Naturally, several factors play a role in their proper growth and development. However, they remain one of the easiest fish to breed, and it’s safe to assume that a male and female that have spent some time together have likely mated.

Featured Image Credit: panpilai paipa, Shutterstock

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