Guppy Fish Size & Growth Chart – How Big Do Guppies Get?

Unlike many other aquatic species, guppies are livebearer fish. This means that the fertilization of eggs takes place internally. The female Guppy Fish then bears the fertilized eggs for about 21-30 days.

When the gestation period is over, the female guppy gives birth to up to 30 fry at a time. Sometimes the number of newborn fry can even reach over 100, but those are rare cases. Guppies are renowned for being prolific breeders. Not only do they give birth to lots of offspring, but they also breed basically year-round.

Guppies are obviously easy to breed. They’re also sturdy and low-maintenance. They don’t have a complex lifecycle, so you don’t have to reinvent the wheel for every stage of their development. There are still minor adaptations you’ll have to make to accommodate guppies in their different life stages. But as long as you got the basics down, it should be a smooth ride. No worries! I’m going to give you all the info you need to keep your guppies healthy.

How Big do Guppies Grow?

This depends on a lot of factors such as diet quality and variety, nutrient deficiencies, water parameters, environmental toxins, and so on. A guppy that isn’t fed an appropriate diet and lives in suboptimal environmental conditions isn’t going to grow to its full potential. That’s why nutrition and water quality are indispensable. Of course, these factors don’t just affect a growing Guppy Fish. They can also affect the long-term health of adult fish.

Usually, male guppies grow up to 0.6–1.4 inches in length (or 1.5–3.5 cm). Females are larger than their male counterparts, reaching around 1.2–2.4 inches (3–6 cm). Guppies reach adulthood at about 6 months of age, at which point their growth either slows down or stops altogether. The male guppy might keep growing for longer, as their tail and dorsal fins are usually larger than those of the females.

Guppy Fish Growth Stages

At each stage of their life, there are some distinguishing traits to help you guesstimate a guppy’s age. This is important, as you need to keep your pets’ age in mind to best look after their needs. I’ve included some useful information about newborn and fry guppies, as well as juvenile, young, adult-age, and old guppies. So, let’s see how you can best care for each of these fish during their development.

– Newborn Guppy

Newborn guppies are tiny and fragile. Right after being born, they’re typically 0.28 to 0.39 inches long (7 to 10 millimeters) and their skin is mostly transparent. Some newborn guppies might also have grey-tinted skin. From the first moment they enter the world, baby guppies are fully capable of swimming and eating by themselves.

Newborn guppies spend most of their time hiding, so you should provide some hiding spots for them. Live plants, rocks, and other decorations are perfect for that. If you don’t have any hiding spots, then you should separate the adult guppies from the newborn. The mother guppy usually eats her fry, especially right after they’re born. If you don’t want the little ones to become live snacks, you’re going to have to move the adult fish to another tank. Other than that, newborn guppies have the same care requirements as fry guppies.

– Fry Guppy

Newborn and fry guppies have still underdeveloped immune systems. To prevent bacterial infections, you’ll have to install a water filter and clean the tank thoroughly at least once a week. Water quality is now more important than ever, so make sure there are no harsh chemicals such as ammonia, chlorine, or nitrites in the water. The temperature should range from 24 to 27 degrees Celsius.

Fry guppies need 8-12 hours of light exposure per day to grow their spines healthily. Not enough light exposure might lead to growth deformities. However, don’t go overboard. More than 14 hours of light exposure per day might interfere with the guppies’ sleep cycle.

During the first 6 weeks of their life, guppies need food every 2-3 hours, or around 5-6 times a day. Feed them a mix of both dry and fresh food and make sure your feed is small enough to fit into their mouth. If you can’t find fry feed anywhere, you can always ground your fish flakes, pellets, and freeze-dried feed into small pieces.

– Juvenile Guppy

After the first month, your guppy fish have entered the juvenile stage. By now, their grey-ish bodies should have developed some color. At this stage, guppy fish measure on average 0.25-0.75 inches (or 1.2 to 2 cm). This is also the stage where sexual characteristics become apparent. You can recognize females thanks to their larger size and the gravid spot on their belly. Male guppies start developing their gonopodium fin.

The juvenile stage lasts for one month. This is the perfect time to diversify their diet to encourage optimal development. Feed them blood worms, freshly hatched daphnia and brine shrimp, spirulina, and other algae pellets. These are great nutritional powerhouses that pack a powerful punch. On top of these foods, you can also continue offering them fish flakes and pellets, but make sure to avoid overfeeding. Of course, the same water, temperature, and light requirements remain important.

– Young Guppy

After about two months, your guppies are officially teenagers! They’ve now entered a new life stage when they become sexually active. If you don’t want any more guppies, now’s the time to separate your male and female fish. At this stage, most young guppies have grown considerably. If the young fish are too big to fit into the adult guppies’ mouths, it’s safe to move them back into your main aquarium.

Young guppies are still developing, so proper nutrition and light exposure are still crucial. Without enough lighting, young guppies can still develop spine deformities before they reach adulthood. Brine shrimp is a nutrient-dense food and should still make up the bulk of their diet. Algae pellets such as plankton and spirulina also provide plenty of vitamins and pigments to keep your fish vibrant and colorful.

As they approach adulthood, young guppies have different dietary requirements compared to juvenile and fry guppies. You’ll have to slightly alter their diet to reduce their intake of fat. The focus should be on protein and plant foods, especially greens.

– Adult Guppy

Guppy Fish reach adulthood at around 6 months of age. Females should now be around 1.2–2.4 inches long, and males should measure around 0.6–1.4 inches. Your aquarium’s probably a sight to behold right now. Adult male guppies are especially colorful and have big tails and dorsal fins. Usually, these fins will keep growing into adulthood as well. But overall, both male and female guppies stop growing in size at this stage.

Their diet should now focus on high-protein fish flakes, but you should still include a variety of foods, both fresh and dry. Even live foods can make a nice addition every once in a while. Avoid feeding adult guppies fats, as these can negatively impact their health at this stage. Adult guppies are fertile until the age of 1.5-2 years old, so if you want to keep breeding them, you have plenty of time for that!

– Old Guppy

In the wild, the average lifespan of guppies is around 2 years old, but when kept in proper conditions, they can live anywhere between 2-5 years old. However, just like any other animal, guppies are going to age. Here are some of the telling signs that a guppy fish has reached old age.

First, older guppies are going to be less active. They might spend more time sleeping or hiding. Besides lower energy expenditure, you might also notice a decrease in their appetite. An older guppy’s color might start to lighten and fade away to a grey tint. As a result of their lack of appetite, old Guppy Fish might become noticeably thinner.

As they reach older age, female guppies might reproduce less often or skip reproduction altogether. In fact, researchers now believe that older female Guppy Fish experience physiological changes similar to menopause in humans.

Wrap Up

You should now be well prepared to breed and care for your new guppies if that’s what you want. Newborn, young, and adult guppies have slightly different needs, but you don’t have to radically change your pet care routine for them. Just make sure that you feed your fish a developmentally appropriate diet, provide enough light exposure, and keep the water clean at all times.

If you don’t have a spare aquarium to house the newborn guppies, try to equip your main tank with plenty of plants and decorations that can double as hiding spots for the little fish. For any additional info on Guppy Fish care, make sure to check my other articles! I’ve written about water parameters and light, heat, and diet requirements in great detail. I also provide tips and solutions for any issues you might have when setting your first guppy tank.