Why Are My Guppy Fry Dying? (With Solutions)

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Watching a guppy female giving birth is undoubtedly exciting. However, keeping guppy fry alive is a different story. I can’t tell how many times I witness their population getting more and more diluted. To solve that issue, I began researching all the possible causes of why guppy fish fry fail to survive.

Most commonly, guppy fry fail to survive due to cannibalism, in which the parents themselves consume the newborns. However, guppy fish fry also die as a result of inappropriate water conditions, such as high toxin concentrations and lack of oxygen.

As we move forward in this article, I will share a few tips to increase the chances of guppy fry survival. I will also present a useful video to you to build a DIY breeding box from scratch, preventing cannibalism among guppy fish.

Also Read: Guppy Fry Care

Why Do My Guppy Fry Keep Dying?

Guppies are livebearers. In other words, unlike some fish that produce eggs that eventually hatch, guppies give birth to live fish. Typically, they are ready to do this at the age of 4-6 months. And once the time comes, they can produce anywhere between 2 and 200 babies per month.

The actual birthing process can take hours. However, in many cases, that is the easy part. Once your fry are finally born, you have to do the difficult work of keeping them alive. They look pitiful in the beginning. They are small, inactive, and deformed. But it only takes a few hours for them to start swimming around and looking for food.

If you’re lucky, your fry will grow into adults which will produce even more fry. However, many of you are not that lucky. It could be that your fry keep dying at alarming rates, and you cannot tell why. 

Unfortunately, fry are quite delicate. They are vulnerable to a multitude of threats, including:

1. Cannibalism

This is probably your biggest concern. Guppy parents have no real interest in their fry. Once a female guppy successfully produces fry, she will not hesitate to abandon them. This is a problem if your fry live in a community tank because they don’t have anyone to protect them from the other adult fish. Most fish will eat anything they can fit in their mouths. 

Because fry are so small, they are a tempting meal for any fish that comes across them. But even if you have a dedicated tank for guppies, adult guppy parents are more than happy to eat their fry. In fact, guppy parents are a more significant danger to their fry than other fish. If you keep losing fry, their parents are probably the cause.[1]

2. Poor Water Quality

Like most fish, guppies need clean tanks to survive. If your tank is dirty, their health will suffer. Prevalent sources of pollution include guppy waste, and dead plants and animals. A dirty tank will compromise the health of your guppies, assailing them with diseases.

Guppy fry are no different. Their small bodies are even more vulnerable to poor tank conditions, the temperature in particular. They haven’t grown up yet to develop a sustainable immune system. Hence, if you cannot raise and maintain the quality of their water, your guppy fry will eventually die. 

3. Oxygen Deficiency

Like most fish, young guppies use their gills to extract oxygen from the water. If your tank has an oxygen deficiency, all your fish will suffer. However, the fry will die at a much faster rate because they are considerably weaker. You could lose most of them before noticing the oxygen deficiency in other fish.

You should raise your suspicion if your guppies are constantly gasping for air. Typically, if they don’t have enough oxygen, your guppy fish will spend their time at the surface of the tank. That behavior also implies to their fry.

4. Inadequate Temperature

Guppies like water with a temperature ranging between 72 and 79 degrees F.[2] This is also the ideal range for baby guppies to thrive. If the water becomes too hot or too cold, your baby guppies will die. As was previously proven, temperature plays a significant role in fish’ susceptibility to diseases.[3] 

If the temperature keeps changing drastically, swinging between hot and cold, the shock will kill your fry; they are too delicate to survive such stress. Guppy fry require consistency.

5. High Chlorine Concentrations

Some people use tap water to fill their tanks since it is a convenient option. But if your tap water has chlorine, which is the case in most households, you have every reason to worry.

Guppies do not like chlorine. It is more than capable of killing adult guppies, which means that it will completely decimate your guppy fry population.[4]

By the time people notice the discomfort in their adult guppies, it is usually too late to save the babies. The main issue, in this case, is that sometimes the adults will survive, and the susceptible fry will die for no apparent reason.

6. Inappropriate Ammonia Range

This isn’t a secret among aquarists; ammonia is bad for fish. Yet, some fish owners believe that their fish can adapt to low levels of ammonia. They are convinced that high concentrations of ammonia are the only enemy they have to worry about.

However, you cannot apply that rationale to guppy fry. As was mentioned above, they are too small and delicate. In small concentrations, ammonia will either kill them outright or compromise their immunity, making them more susceptible to illnesses. 

Naturally, high levels of ammonia will also compromise the health of your guppies’ fry. That typically happens once you permit uneaten food, dead fish, and dead plants to rot in the tank. Dirty filters can also elevate the levels of ammonia.

7. Inadequate Feeding

Many aquarists worry about overfeeding their guppies. With the fry, your biggest challenge is underfeeding. Guppy fry should be fed five or six times a day. Besides maintaining this frequency, you have to break their food into the smallest sizes possible. 

Otherwise, they won’t be able to fit anything you add to the tank in their mouths. This can lead to starvation.

Unfortunately, some aquarists realize too late that the food they keep adding to the tank is going uneaten. It may even take longer to realize that the fry have been dying because of this very reason.

Also Read: Guppy Fry Not Growing

How Do I Keep My Guppy Fry Alive?

Believe it or not, the key to keeping your guppy fry alive is to maintain the most optimal conditions in their tank. If you care for adult guppies, you can care for their young ones, though it takes some practice.

Keeping guppy fry alive involves the following steps:

  1. Raise the guppy fry and their parents in separate tanks.
  2. Add plants and decorations to provide the fry with hiding spots.
  3. Use a relatively large tank and avoid overcrowding.
  4. Maintain a stable temperature that ranges between 72 to 79 degrees Fahrenheit.
  5. Feed the fry ground live food, five to six times a day.
  6. Use a delicate air stone and illuminate the tank eight hours a day.
  7. Maintain a pristine tank by removing dead plants, debris, and waste.

1. Separate the Fry

Before you can start working to maintain your fry’s health, keep them safe from the fish that might eat them. That includes their parents; you are encouraged to keep the mother in a separate tank once it becomes clear that she’s about to give birth.[5]

Female guppies on the verge of giving birth tend to hide a lot. They may also find refuge near the heater. Once the fry are born, move the mother back in the main tank, while leaving the fry in a separate tank for a few weeks. They are more likely to survive if they don’t have to worry about bigger fish eating them.

  • You may also build yourself a breeding box, as is described in the following YouTube video. That will ensure your female guppy is immediately separated from her fry after giving birth:

2. Add a Few Plants

Some people can afford to buy a breeder box for their fry to inhabit. Other people have to make do with a single community tank.

But even in such cases, you can increase the chances of your fry surviving by adding plants, rocks, decorations, and basically any item the babies can use as a hiding spot.[6]

Guppies are vulnerable because they are small. But their small size also makes it easier for them to hide. Some fry are bound to wander out of cover from time to time. But you shouldn’t expect all of them to survive. Community tanks are dangerous places. One or more fish will eventually eat one or more fry.

3. Use a Relatively Large Tank

You should avoid overcrowding since it leads to pollution and oxygen deficiencies. If your tank is overcrowded and you prioritize your young guppies, reduce the number of adult fish. If you have the means, get a much bigger tank.

Young guppies cannot effectively stay out of sight in a small, crowded tank. They will eventually attract the attention of hungry adult fish. Needless to say, the most suitable solution is to grow the guppy fry entirely on their own.

4. Ensure Stable Temperature

As was mentioned earlier, you should maintain the temperature within the appropriate range of 72 to 79 degrees Fahrenheit. Don’t rely on the ambient temperature. Get a heater if possible, preferably of high quality. This is the only way to maintain consistency. 

Ideally, the temperature should be around 74 degrees F. Do not permit wild swings to occur. Stability plays a considerable role in keeping your guppy fry healthy. If you perform water changes, make sure that the water you pour is within the desired range.

5. Feed the Fry Properly

As was mentioned above, you need to feed your guppy fry five or six times a day.[7] They can survive on the same meals as their adult counterparts. But you must crush their food into small pieces that they can fit in their mouths. They need powdered items. 

You may use two teaspoons to grind their food. Then, observe the fry and see if they consume their meals. If there are leftovers, make sure that you thinner their food a little more. Also, try to give them a variety. Live foods such as brine shrimp and microworms work best.

6. Provide Light and Oxygen

Guppy fry require light.[8] Install lighting in their tank that will illuminate them for at least 8 hours a day (but no more than 14 hours).[9] The presence of light keeps the fry active, and that is good for their growth. But you should turn the light off at night. This will allow them to rest. The objective is to create a day/night cycle for them.

Also, young guppies cannot survive in an oxygen-deficient tank. This is why you are encouraged to add a mild air stone. A decent filter can also create enough of a disturbance in the water to ensure that the oxygen is sufficiently distributed throughout the tank.

When it comes to selecting a filter, avoid powerful devices that create a harsh flow. They will either suck the fry in or tire them out. Get the sponge type. It is worth noting that a fry tank doesn’t need a filter. If you don’t know how to identify the right filter for your fry, don’t bother getting one.

7. Create an Ideal Environment

Try to maintain a clean tank by changing the water at least once a week. Also, remove dead plants and animals, not to mention leftovers and waste. Ensure that the ammonia levels are at zero. If you think you need one, get a filter. If tap water is your only option, take the time to dechlorinate it before adding it to your fry tank.

If your fry live in a community tank, when some of the adult fish fall sick, you should take them out. Do not add medicine to the community tank to treat them. Drugs that treat adult guppies will probably kill the fry. Merely take the sick fish out. This will prevent their sickness from jumping to the fry.

How Many Guppy Fry Will Survive?

It is difficult to tell. Some people will tell you that at least half of your fry will survive. Others will tell you that they can only ever save three or four fry at a time. However, that only happens in situations where the aquarists are still new to guppy fry.

Generally, it is more than possible for all your guppy fry to survive. It is merely a question of your abilities and experience. Following the tips above will make it much more likely to happen. However, getting around the learning curve is nearly impossible. 


Guppy fry fail to survive mainly due to cannibalism. Unlike other creatures in nature, guppy parents have no interest in their offspring. More than that, they are likely to consume their babies when given a chance.

To prevent this from happening, I highly recommend raising the fry in a separate tank. You should also be prepared once the female is about to give birth. Move her away as soon as you can. If possible, getting a breeding box is probably your best option.


  1. https://pets.thenest.com/save-baby-guppies-community-tank-3621.html
  2. https://pets.thenest.com/temperature-should-aquarium-guppies-12350.html
  3. https://jeb.biologists.org/content/jexbio/201/2/165.full.pdf
  4. https://guppyexpert.com/guppies-keep-dying/
  5. https://pets.thenest.com/mother-guppy-stop-eating-her-fry-4107.html
  6. https://mrfishkeeper.com/guppy-babies/
  7. https://small-pets.lovetoknow.com/fish/rearing-guppy-fry
  8. https://www.wikihow.com/Help-Guppy-Fry-Grow
  9. https://www.wikihow.com/Care-for-Baby-Guppies