How Big In Size Do Guppy Grow?

One of the major reasons why guppy is a top choice for aquarium owners is because they are easy to maintain, and if given enough space, fed well, and served with the right water parameters, they can grow into beautiful and healthy adults. How big in size guppies grow is dependent on these factors, the sex, as well as some genetic variations.

If you keep your guppies under favourable conditions with proper feeding and a good genetic background, they can grow to reach an average size of 1.5-2.5 inches. On few occasions, some rare genetic strain of guppies can even grow up to 3-3.5 inches. 

How Big In Size Do Guppy Grow

This variation in size is largely influenced by sex because the male guppies are generally smaller than female guppies. Male guppies often reach a maximum size of about 1.5 inches while females can grow up to 2.5 inches or more. This feature and the bright colours of male guppies are part of the major features that can be used to distinguish between the sexes.

Why Do Guppies Stop Growing?

Aside from the natural phenomenon that makes animals stop growing at a certain age, some environmental and genetic factors can also limit the growth of guppies.

One of the major things that can limit the growth of guppies is aquarium space.  Lack of space or overcrowding of tanks can make the guppies stop growing particularly during their developmental stages. Similarly, incompatible tank mates, stress, improper male to female ratio, and so on can also limit the growth of guppies.

Poor water conditions can also limit the growth of guppies. If the water and environmental parameters of the tank are not within a favourable range, it can limit the development of the guppies. These factors include temperature, oxygen level, toxins, as well as pH.

Poor feeding and genetics are also factors that can dictate the growth of guppies. High-quality food with variety can ensure that you supply your guppies with all necessary nutritional requirements. Similarly, the genetic pedigree of the guppy can affect the growth of the fish. However, you can breed guppies for specific traits including size, colours, and even patterns.

When Do Guppies Reach Maximum Size?

The development of guppies is in stages, from guppy fry down to adult. Guppies often stop growing when they reach the adult stage. They usually reach the adult stage with full physical and sexual development after 6 months. At this stage, they can freely breed, exhibit all characteristics of an adult, and might not add any more inch to their size.

Although there are some rare occasions [mostly influenced by genetics] when guppies still add more size after this period, but it is very rare. Males can however, add longer tails and fins while also featuring brighter colours.


Compared to other aquarium fishes, guppies are relatively small with male guppies even smaller in size than the females. With a good diet, good water parameters, favourable environmental conditions, and selective breeding, you can be sure of creating a maximum-sized and colourful guppy. And with all these factors in check, you can expect them to reach this maximum size in about six months.

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