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Can I Leave Guppy Fry In The Tank? Will They Survive?

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The first question that popped into my head after realizing that my guppy fish was pregnant was whether I could leave the fry in the community tank. That was a few years back, and ever since, I gained some experience in this field.

You can leave guppy fry in the community tank, but only a few will survive without taking the proper measures. These include providing a sufficient amount of hiding places, such as plants and decorations. Otherwise, it is better to use a breeder box or a breeding tank.

As we move forward, I will share some tips to help you grow guppy fry in the community tank, alongside adult fish. I’ll include some products that helped me keep my guppy fry alive and an excellent video on how to make your own aquarium divider.

Still curious? Feel free to check my complete guide on guppy fry. There, I discussed how to care for guppy fry, what they eat, how often to feed them, their growth stages, and much more.

Can I Leave Guppy Fry In The Community Tank?

Leaving guppy fry in the main tank is problematic because the adult guppies will eat them. Admittedly, guppies are just like people. They have unique personalities.[1] Therefore, you cannot expect them to react the same way in every situation.

You will find plenty of stories about aquarists whose adult guppies coexisted with their offspring if you look for them. But those anecdotes are the exception rather than the rule.

It is uncommon for all the fry in an aquarium to survive to adulthood. As I previously discussed, their survival rates vary between 0 and 40 percent

Various factors can affect their mortality rates, the most prominent being the temperature, which should be kept between 78 and 80 degrees F. However, their chances of survival plummet once you abandon them in the main tank. 

To be clear, this isn’t necessarily a bad thing. If you don’t want the guppies to overwhelm your aquarium with their numbers, the best option is to keep them in the same aquatic space as their parents.

The adult guppies will make quick work of their babies, ensuring that only the smallest number survives to adulthood. This will prevent the guppy population from running amok.

But if your goal is to raise as many guppy fry as possible, you cannot leave them in the main tank. The main tank exposes them to filial cannibalism. 

Why Do Adult Guppies Eat Their Babies?

Experts in this field have blamed this practice on numerous factors, including:

1. Guppy Fry Are Considered A Food Source

Some have suggested that guppies eat their young, not out of malice, but because they cannot differentiate baby guppies from food.[2] Their size is the biggest challenge. Guppy fry are just 0.6mm at birth, and fish tend to eat whatever fits in their mouths.

A 0.6mm guppy fry will easily fit inside the mouth of an adult guppy. In that regard, the parents are not really at fault. The creatures are doing what nature programmed them to do.

As I previously discussed in my guppy fry growth stages guide, those little creatures reach the juvenile stage only after 30 to 60 days. Only then do they reach a size that allows them to go with adults.

Adult guppies will eat their offspring more vigorously when resources become scarce. They will use the babies as an energy source.[3]

The creatures are also more likely to eat the fry to reduce the population if the volume of food in their aquatic environment has fallen to dangerous levels.

They are just as concerned about the population as their owners. They don’t want to overwhelm the tank with new guppies. This won’t stop them from breeding.

2. Guppy Fry Are Easy Prey

Guppy fry are easy prey as they cannot fight back. Every predator in the animal kingdom will target the most vulnerable member of any species they come across.

Humans are the same. They would rather buy meat from the market than hunt and kill an animal in the jungle. Guppies are no different.

3. Keeping The Bloodline Clean

Some aquarists have argued that guppies want the strongest among their kind to survive. As such, they will target unhealthy fry, especially babies with genetic illnesses and deformities.[4]

This keeps their bloodline clean, preventing genetic disorders from persisting through the generations. They want the healthiest guppies to pass on their genes. 

4. Stressed Guppies Are Aggressive

Stress can make peaceful species aggressive, forcing them to turn on the weakest members of their society. Many factors can induce aggressive behavior in guppies. 

If you force the guppies to inhabit a stressful environment with extreme temperatures, an unstable pH, and dangerous ammonia levels, it will take its frustration out on the fry because they are weak.

How Do You Stop Guppies From Eating Their Babies?

Most people separate guppy fry for 6 to 8 weeks, as I previously discussed here. After this period, they are considered juvenile and reach a size of one to two inches. Being that big, they can no longer fit in their parents’ mouths. 

But some aquarists expect guppy fry to share a tank with their parents. They argue that the threat their parents pose makes the guppies stronger. It ensures that only the strongest survive.

On the other hand, keeping the fry in breeding tanks weakens them. After all, baby guppies in the wild don’t have this luxury. They don’t have separate nurseries to protect them from predators.

If you hold this attitude, and you want to maximize the survival rate of your fry without placing them in a separate tank, these methods and tricks will help you:

1. Fill Your Aquarium With Plants

Add as many plants as your tank can accommodate. Baby guppies need hiding places. They can use floating plants and decorations to stay out of sight. This increases their chances of surviving. 

I personally recommend the JIH Aquarium Plastic Plants And Cave Decor Set (link to Amazon). It comes with one cave ornament and six pieces of plastic plants. Besides its outstanding appearance, this decor set is highly efficient in terms of hiding places.

Though, plants and ornaments cannot provide any guarantees, especially if your tank has predatory creatures that actively hunt weaker fish. 

Some people use light to guide newborn fish to sanctuaries such as caves where predators cannot reach them.[5]

2. Use A Breeder Box

A breeder box is different from a breeding tank. A breeding tank is a separate tank, while a breeder box sits inside the main tank. You can place pregnant guppies in breeder boxes shortly before they give birth. 

Once the babies escape the birth canal, they can run to a safe zone below that uses a mesh wall to protect them from the mother.

You can keep the babies in the breeder box for several weeks until they are too big for their parents to eat. Breeder boxes are convenient because you don’t have to prepare a separate tank.

More importantly, you don’t have to acclimate the babies to the conditions in the main tank. They will spend the first few weeks of their lives in those same conditions until they are large enough to live outside the breeder box.

For my guppies, I got the Capetsma Fish Breeding Box (link to Amazon). It comes in three sizes, so you can choose the one best fits your aquarium. But make sure you take out the mother after she has done giving birth.

3. Install An Aquarium Divider

If you hate breeder boxes because of their reputation for inducing stress in pregnant guppies and stunting the growth of their offspring, use a divider. Like the breeder box, a divider allows aquarists to keep the fry in the main tank. 

You don’t have to acclimate them once they are big enough to live with their parents. The divider separates the guppy fry from the adult fish in the community aquarium. 

This is actually my favorite choice. From what I have found, this method causes the least stress in pregnant guppy fish. For your convenience, here is an illustrated Youtube video that shows you how to make your own aquarium divider:

4. Create A Comfortable Environment

I highly recommend that you maintain the appropriate conditions in the aquarium. Adult guppies are less likely to attack their offspring if they are happy. 

Start by giving them plenty of room. Don’t give them any reason to think that they have to reduce the population. As a rule of thumb, you’ll require half a gallon for each guppy fry when they are born.

It is just as essential to give them plenty of food. Starving guppies will eat whatever they can, including their babies. Satisfied guppies are more likely to leave their offspring alone.

Here is a guide that I previously wrote on what do guppy fry eat. Following this will ensure that your guppy fry grow healthy and at the right pace. I also dedicated an entire article to how often you should feed guppy fry.

These are the best water parameters for guppy fry:

  • Temperature: 78-80 degrees F 
  • pH: 6.8-7.6 
  • Hardness: 8-12 dGH 
  • Ammonia: 0 ppm 
  • Nitrites: 0 ppm 
  • Nitrates: <20 ppm

To measure the pH, ammonia, nitrates, and nitrites, I personally recommend getting the API FRESHWATER MASTER TEST KIT (link to Amazon). This bundle lasts for eight hundred measures, so it is definitely worth the investment.

You should also pick friendly tankmates such as Kuhli Loaches, Nerite snails, Cherry shrimp, and small Corydoras. These species are considered docile and are not likely to attack adult guppies or their fry.

If you found this article helpful, these may also interest you:

Conclusions

Guppy fry can survive in a community tank, but they require some hiding places. In a bear tank, all the guppy fry are expected to be eaten. That is why I suggest introducing plenty of plants and decorations. 

Another option is to install a divider. That method is superior to breeder boxes as it gives your fish more room. 

Breeder boxes can be pretty stressful, especially to the pregnant guppy. If you still wish to use those, make sure you remove the mother after she has done giving birth.

References

  1. https://www.washingtonpost.com/news/speaking-of-science/wp/2017/09/25/scientists-spent-a-month-terrifying-guppies-to-prove-that-fish-have-personalities/
  2. https://www.lifeforfish.com/how-do-i-stop-my-guppies-from-eating-their-babies/
  3. https://urbanfishkeeping.com/do-guppies-eat-each-other/
  4. https://learnaboutpet.com/do-guppies-eat-their-babies/
  5. https://onlinelibrary.wiley.com/doi/10.1111/are.12129