How long do guppies take to grow? Time Scale | Size | Growth Rate

Undoubtedly, the Guppy has to be one of the most easily recognizable and attractive tropical fish in the hobby. They are one of the world’s most widely distributed fish, and incredibly popular in the home aquarium.

A peaceful fish that is active and full of color the Guppy prefers to be kept in groups, the larger the better. At around two inches when fully grown they are a smaller species, but one that is full of charm. They do, however, as with any living creature, take time to reach their two-inch potential, which leads us to the question ‘how long do guppies take to grow?

How long does it take for guppies to grow? Several factors can influence the growth rate of Guppies. Most will reach adulthood within 6 Months. Full size for a male is 1.5-1.8 Inches and 2-2.5 Inches for females. Jumbo Guppies are the exception which can grow up to 5 Inches and take 12 Months to be fully grown.

Guppies live a simple life with a very simple life cycle. This does not mean though that growth rate can be specifically pinpointed to the millimeter. We can, however, put together a fairly comprehensive guide to Guppy growth that can give us a good idea.

This stunning adult Guppy will have grown into adulthood within 6-12 Months

The Fry Stage

Guppies are livebearers meaning that they do not lay eggs. Rather, the male fertilizes the female who then becomes pregnant for around thirty days. Guppy fry, when born, are free swimming and will only be a few millimeters in size.

To achieve maximum potential growth before they reach the next step in their life cycle Guppies need to be well fed. They will eat the same foods as their parents, like tropical flake, but will need it crushed to a fine powder.

Read our complete guide for feeding your Guppies a complete and balanced diet.

Live food such as brine shrimp is also hugely beneficial to achieving maximum growth. As is the yolk of a hard boiled egg and leaving the lights on in the aquarium for 12 to 16 hours a day.

Guppies remain fry for approximately one month.

The Juvenile Stage

By the time Guppies become juveniles they will have started to gain some color and display their sex. Females will be much larger with their gravid spot clearly visible. Males, on the other hand, will show smaller tails and have started to form their gonopodium.  

Juveniles should be ¼ to ¾ of an inch in size with this stage in their life being the most important with regard to growth. Foods should be the best that you can feed them and their water should be pristine.

We feed our Juvenile guppy Hikari USA Guppy Food which you can purchase by clicking the image or the link here.

Brine shrimp, blood worm, spirulina, plankton, beef heart, and high-quality flake are the foods recommended at this point. Small daily water changes would also be beneficial.

Guppies remain juveniles for up to two months.

Painting of a pair of guppies- fishkeepingforever
Beautiful Picture Of A Pair Of Guppies

The Young Stage

At around two months of age, Guppies become sexually active, but it is not recommended that you breed them at this time. Rather, it is beneficial for the Guppies that you separate males from females at this young stage. This is so that they can focus their energies on feeding and growth instead of reproduction.

Feeding young Guppies is different from feeding juveniles in that they now need a lower fat intake. To achieve this, they should be offered more proteins and greens, with brine shrimp making up the larger part of their diet. Young Guppies should be between ¾ inch and 2 inches in size.

Guppies remain young until they are six months old.


At six months old Guppies are considered as having reached adulthood and now growth will slow down considerably before stopping. Depending on genetics and condition their size should be 1 ½ to 2 inches.

It is, however, possible that though the body has stopped growing the tail and fins may continue to do so. This will depend highly on their genes and that they are fed a high quality and nutritionally balanced diet.

Guppies will be adults, translated to their lifespan will be, approximately 2 to 5 years. They are, interestingly, only fertile between the age of 1 ½ to 2 years.

A large group of Guppies are often called Schooling groups but are Guppies really schooling fish? Read what’s the difference between schooling and shoaling fish which is explained in one of our articles.

The Jumbo Guppy

As with most things, there are a couple of exceptions to the Guppy growth rate ‘rules.’ The first is the Jumbo Guppy which exceeds, and sometimes greatly, the 2-inch size at adulthood.

Little is actually known about the Jumbo Guppy which usually grows up to 2 ½ to 3 inches but can reach around 5. There are, however, two theories which stand up to scrutiny.

The first is that the Jumbo Guppy is a product of large specimens brought in from Asia and bred in home aquariums. Whilst the other is that they are the result of separating the male and females at the ‘young’ stage.

Whichever is the reason it does mean that the growth rate will vary from the aforementioned. Larger sizes should be achieved at each stage, though the fully grown size will still take as long.

Stunted & Slow Growing Guppies

The second exception to the Guppy growth rate ‘rule’ is the stunted or slow-growing Guppy. Both of these can be caused by just two factors, which are bad breeding, and more commonly improper care.

All fish need a variety of things in order to grow and thrive. As a general rule of thumb these are:

  • The correct diet
  • A large enough aquarium
  • The correct water parameters
  • The appropriate environment (tank mates/decor)

Without these essential things being provided a Guppies growth rate will be severely compromised.

Conclusion: How long do guppies take to grow?

To finally answer the original question of ‘how long do Guppies take to grow?’, the answer will all depend on the type of care they receive. However, Guppies that are well fed, well housed, and well looked after in general should be fully grown by six months old.

We have a great article explaining why guppies make great pets. It’s worth a read if you own a tropical fish tank and you’re looking for a special community fish.