Guppy fish eating their own offspring is a widespread phenomenon in home aquaria, and first-time breeders are always recommended not to leave guppy fry in the same aquarium with adult guppies.
But what is it about guppies that they eat their babies, and can you do anything about it? In this article, I shed light on the various reasons why this happens among guppy fish, and what can you do to prevent them from eating their babies.
Unfortunately, if you leave guppy babies in the same tank with adult fish, the adults will end up decimating their own fry. This behavior is known as filial cannibalism, and it can be found in many species across the animal kingdom as it is not limited to guppy fish.
But why exactly do guppies eat their fry and how to prevent them from doing so if you want to breed guppy fish?
Why Guppies Will Eat Their Fry?
Some fish species such as angelfish are known to take care of their fry and help them grow. But even these fish that exhibit parental care will at times eat their own fry.
After giving birth to their offspring, guppy fish will not exhibit any parental care and if left in the same aquarium with the fry, they will mistake them for food and eat them.
It’s a puzzling behavior that has long preoccupied researches. According to some, filial cannibalism is a result of a spill-over response prompted by stress factors, which enhances the self-preservation instinct of fish.
However, this isn’t a satisfactory explanation because the same behavior can also be observed in fish that aren’t kept in stressful conditions.
Another explanation for this type of behavior may be that by eating their own offspring guppy fish are weeding out fry that are less adept at surviving.
This can happen either because guppy babies lack the necessary survival traits (e.g. can’t easily hide from predators) or because they’re genetically weak offspring.
Therefore, adult guppies are increasing the survivability of the species as a whole by weeding out weak specimens.
A further explanation is that by eating her own fry, the female guppy is replenishing her fat storage. This, however, doesn’t explain why male guppies will eat their own offspring.
As you can see, there isn’t a clear consensus to filial cannibalism happens, and it may be that the explanation is a combination of self-preservation and the perpetuation of strong offspring.
Luckily, you don’t need to accept this situation as there are various methods to prevent guppies from eating their fry.
How to Prevent Guppies Eating their Babies
There are multiple ways to prevent guppies from eating the fry and all focus on finding ways to separate guppy adults from guppy babies.
Here are three ways to ensure the survivability of guppy fry:
1. Breeding Box
The breeding box is a plastic container or mesh designed to be installed into your main aquarium.
The breeding box will keep the pregnant female guppy fish separated from the other adults. Water will flow in and out of the breeding box, but adult fish will have no access to it.
As soon as the female guppy gives birth, she should be taken out of the breeding box to prevent her from eating the fry.
The fry will be safe in the breeding box as other fish won’t be able to get in nor will the fry be able to get out.
This method is great if you don’t yet have a separate aquarium set up for the fry and your current aquarium is large enough to comfortably accommodate a breeding box.
Plus, you don’t need to stress about matching the water parameters of the main aquarium with the tank you set up for the fry.
Careful with the breeding box, however! Fry should not be kept in it longer than two weeks as their growth can be stunted.
At two weeks, you can release guppy babies either into the main tank or place them into their own aquarium.
2. Separating Pregnant Female Guppy
While the breeding box is also a way to separate the pregnant female guppy, you can also set up an entirely different tank for it.
As the female is preparing to give birth, you should place her into a separate aquarium, where she can give birth, and then you can extract her, leaving only the fry in the tank.
A rounded abdomen, reclusive behavior and a V-shaped abdomen signal that the female is preparing to give birth.
Of course, this is a more expensive method since you’re required to set up a new tank with equipment required for a guppy fish tank (heater, filter, lights, etc.).
But if you’re breeding guppies for profit, this an investment that you must make to ensure the survivability of your fry.
When transferring the female guppy fish into the new tank, make sure that the water parameters (temperature, hardness, pH, etc.) of the new tank match that of the home aquarium.
After the pregnant guppy releases the fry, you should remove her as soon as possible to prevent her from eating her babies.
3. Lots of Live Plants and Hiding Places
A third method to prevent fry from getting eaten by adults is to ensure that your aquarium has a lot of live plants and hiding spots that fry can use to elude hungry adult fish.
Having live plants in the aquarium has benefits that reach far beyond offering cover to fry.
Plants can also be a source of food for fry and help control the level of toxins in the aquarium.
Guppies will also enjoy the soft algae that grows on these plants.
This method is not as fail-safe as the other methods I described, especially considering that not all guppy babies can hide and go unnoticed.
You shouldn’t use this method if you want to breed guppies professionally.
It’s more suited for when your guppies breed, even though you weren’t expecting them to do so, and you don’t know what to do with all that fry.
If you don’t want to remove them and care for them, you can leave them in with the parents and hope at least some of them will be able to hide until they’re large enough to no longer end up getting eaten by adults.
Of all the methods I described to save guppy fry, I prefer setting up a separate aquarium and transfer the pregnant female guppy to that aquarium until she gives birth.
After she gives birth, I can easily extract her and continue caring for the fry myself.
For best results, I set up a feeding schedule and feed guppy babies 5 times a day with a varied diet that includes a mix of live foods (brine shrimp, daphnia, vinegar eels), fry flakes, and beef heart paste.
There isn’t a clear answer to why guppies eat their fry. It’s something you must come to terms with as soon as possible and familiarize yourself with the methods you can apply to save the fry.
I hope the methods I described will help you save as many fry as possible and that you don’t get discouraged from breeding guppies and caring for their fry.