Why Do Guppies Eat Their Babies? (and how to prevent it!)

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Why do guppies eat their babies? Guppies display a behavior known as filial cannibalism which results in an adult animal eating her own babies immediately after birth. Guppies show no parental care for their fry and do not distinguish their own offspring from any other fry in the vicinity.

Guppies are one of the most popular tropical fish in the fish-keeping hobby. They are kept worldwide and have been popular since the late 1960s. I first started keeping and breeding guppies over 30 years ago.

One of the reasons they are so popular is because they are so easy to breed. Give them a box of water to live in, feed them well and they will produce more.

What Is Filial Cannibalism?

Filial cannibalism is the phenomenon when a female animal gives birth, then turns around and eats its own newborn offspring. There is much debate amongst researchers as to why some animals do this.

One credible suggestion, which certainly makes sense in terms of guppies, is that the female is only eating those babies that don’t possess the instinct to hide immediately after birth. She is only eating the weak babies and by doing so, strengthening the gene pool overall for future generations.

How Do Guppies Reproduce?

Guppies are a live-bearing species of tropical fish which originates from coastal streams in northeast South America. As a live-bearing species, guppies do not lay eggs. Instead, the eggs are fertilized by the male and then retained inside the female guppy’s body whilst they develop.

When guppy fry are born, they are free-swimming and totally independent. Unlike some members of the Cichlid family, like Angelfish, Guppy parents take no responsibility for their young at all.

How Many Babies Do Guppies Have?

The number of babies a female guppy gives birth to is directly related to her size. Young small female guppies may produce as few as 6 babies at a time. Older, larger female guppies can give birth to as many as 200 babies at any one time.

How To Prevent Guppies Eating Their Babies?

Whether you are breeding for fun or for profit, there are a number of techniques you can use to increase the number of guppy babies that survive. The technique you choose may be dictated by available space or money you are prepared to invest.

1. Using Breeder Boxes

Breeder boxes are plastic boxes that float in the aquarium. The female guppy is moved to the breeder box just prior to her giving birth. I have had good success using the KIEYYRYT Fish Breeding Box (you can check the current price on Amazon here).

Once the female is in the breeder box she is safely separated from the other fish in the aquarium. The female will now remain in the breeder box until after she gives birth to the babies.

Inside the breeder box, there is a grid. When the babies are born they will drop down through the grid into a second section, safely away from the female. Once the female has finished giving birth she can be removed from the breeder box, leaving the babies floating in the breeder box safely away from the adult fish.

The baby fish live in the breeder box for the next few weeks until they grow large enough that the other guppies no longer consider them as food.

2. Using A Separate Aquarium

If space allows it, moving the pregnant female to her own, separate aquarium just prior to her giving birth will increase the number of fry that survive. She can be moved and then left in the new aquarium until she has finished giving birth, then moved back.

Before moving the female, make sure the temperature and pH of the new tank are the same as the original tank.

3. Using A Heavily Planted Aquarium

Another way to reduce the number of guppy fry that are eaten is to make sure your guppy tank is heavily planted with live plants. A tank full of wisteria or java moss will help reduce the number of fry that are eaten dramatically.

If you don’t want to use live plants, check out these fake ones on Amazon, they have worked well for me in the past.

Guppy fry are programmed to head for cover the minute they are born. By providing the cover they are looking for you tip the scale of odds in the fry’s favor.

The video below shows what a tank full of java moss might look like. Any guppies born in this tank have an infinite number of places to hide from hungry adult guppies

How Do You Know If A Female Guppy Is About To Give Birth?

Throughout the female guppy’s pregnancy, her belly will grow. In the few days leading up to the actual birth, the female starts to look ‘boxy’. Her belly starts to square off at the bottom. She will develop two dark patches at the back of her belly, just below her tail. These dark spots are known as ‘gravid spots’. There is no mistaking the look of a female who is just days away from giving birth.

One thing to bear in mind, whatever your reasons for breeding guppies, you don’t necessarily want EVERY baby to survive. Some guppy fry will just be genetically weak and not destined to survive. It is just a sad part of breeding fish.

In Conclusion

All fish just seem to find guppy babies irresistible! If you have a community tank that includes a few guppies, over time the population will increase slowly as 1 or 2 babies survive from each pregnancy.

If you actively want to increase your guppy numbers, consider using one of the methods above. Just bear in mind, the more guppy babies you save, the more adult guppies you will have in 3 months’ time. It is easy to get overrun with guppies!

About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James

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