Why Your Platys Keep Having Babies (And What To Do)


You might be wondering why your female Platy is suddenly pregnant when there’s no male around it. The answer to this mystery is quite fascinating.

Female Platy gets pregnant months after male contact.  Female live bearers like Platies can store up a male’s sperm inside them for up to 6 months.  This is simply known as female sperm storage.

The situation might be like this: you brought home the female from the pet store where it was already exposed to a male.  Or you might have removed it from a tank with males months ago.  Or, the male that used to live with it has already died, but your Platy could still have babies.

Can Platy Have Babies Without A Male?

Platies can’t breed without a male.  They have to have contact at least once in order for the female to get pregnant.

Scientists have been studying the sperm-storing ability among fish particularly on another live bearer that hoards sperm: the Guppy.  Although from a different family, Guppies and Platies are both very popular tropical freshwater fish known for their hardiness despite their small size.

How Long Do Guppies Store Sperm?

In the case of Guppies, they can store male sperm inside them for up to 10 months.

Female Guppies outlive males by about a year.  Sperm storage then could be a coping ability so these strong females can establish their own colony even without a male present.  They are also larger than male Guppies. 

But let’s go back to Platies.  While it is true that female Platies are an inch larger than males—growing up to 2.5 inches long—there is no extensive study or properly documented evidence that female Platies live longer than their male counterparts.  But they do have female sperm storage ability just like Guppies do.

Platies and guppies aren’t the only species with female sperm storage ability. 

There was a recent discovery that a brownbanded bamboo shark stored male sperm in her for 3.5 years before deciding she wanted to have a pup.

That’s a really cool way of preserving your species.

Other animals like some species of rattlesnakes, octopi, beetles, fruit flies, turtles, snails, and even chicken can store sperm for long periods of time, even up to years for some.  Researchers believe this is a very useful ability especially for females that aren’t at the peak of their ovulation cycle yet, or for females whose males died or was separated from the females shortly after mating. 

Platies in a tank
Why Your Platys Keep Having Babies?

Female Platies, just like guppies, are equipped with a specialized cavity inside their ovaries that keeps their mates’ sperm alive by nourishing it.  Further studies in guppies however, show that sperm loses its virility with age, making for less healthy babies.  But the ability is like insurance, giving the species the power to reproduce even without its mate.

It also gives the female Platy a choice to choose which ones would create the best and strongest babies.

Who needs a sperm bank when she has one inside her, right?

How Do Platys Mate?

While the ability of the Platy female to store sperm is fascinating, mating happens fairly similar to most other livebearer fish.

When Platies reach maturity at 4 to 6 months, the males will begin to chase the females and perform a “twitching” dance ritual to impress her with his energy.  Female Platies look for highly-colored, energetic males with large bodies.  But even if she doesn’t like the male chasing her, she might get exhausted and cave in.

The male Platy uses his anal fin or gonopodium to latch on to the female and try to tuck in a packet of fluid in her.  He will repeat this several more times until he’s succeeded.

Males typically chase females to the point of exhaustion, which is why it is important to have a 1:3 male to female ratio of Platies in the tank to minimize female stress.

It is instinctively natural to select the best traits in choosing a mate.  This is why it’s top priority for males to constantly “strut” in front of females in hopes of being entertained by her.  Bigger, healthier fish daddies produce bigger offspring with higher growth rates.  Female offspring have larger reproductive output when they mature.

Do Platys Breed Easily?

It’s very easy for Platies to breed.  Just leave a mature male Platy with some females and they will eventually get pregnant.

It’s not actually a question of if, but when.  If you need more information about how to care for pregnant Platies, check out our post about it here.

How many Platy fry are born?

Each batch of Platy fry average 20 to 40 in number, but they may give birth to as much as 80. 

Platy fish keep having babies
Do Platys Breed Easily?

These aren’t much compared to other fish because Platies do not lay eggs and thus have a smaller space for developed fry in their wombs.

Should baby fish be separated?

If there are parenting awards, Platies will never win any of them.

Platies aren’t very good parents and in fact tend to eat their fry.  It is best to have the female Platy give birth in a breeding tank and then put her back in the main tank once she’s done.

It’s also not advisable to keep the babies in the main tank unless it’s large enough and is heavily planted.  Otherwise, adult fish (not just Platies) will eat the babies and none will be left—unless of course, this is your intention.

But if you plan to keep them, try and take them out of the main tank.

How do you transfer fry from one tank to another?

If you’re already in that predicament, there are a few ways you can save the baby Platies.

You can catch Platy fry from your main tank with a fine mesh fish net.  Use it gently to scoop up the fry but leave the bottom of the net under water so as not to stress the babies.  Then use a small cup to scoop the fry out of the net and into your growout tank.

The idea is to never stress them out by removing the water completely. 

Why are my Platy fry not growing?

Now that you’ve decided to take care of your fry, you need somewhere to put them in.

Stress and malnutrition are the main causes of stunted growth in Platy fry.  You cannot keep baby Platies in very small containers as there won’t be enough room for them to swim and build muscles.

If they’re in the right kind of growout tank and yet they’re not growing as they should, it must be what you’re feeding (or not feeding) them.

What do you feed Platy fry?

The first foods you can feed Platy fry should be nutritious yet small enough to fit their mouths.

Platy fry benefit the most from eating baby brine shrimp, daphnia, crushed yolk of a boiled egg, and other similar protein-rich food.

If you don’t have a lot of time to prepare these, there are also good commercial alternatives such as Hikari First Bites, or you can serve them crushed up flakes. 

Remember, these fish are hardy, but always try and give them your best so you get maximum growth and best colors.  Make sure the flakes are high in protein and less on the fillers (wheat-based ingredients) for optimum nutrition.

When can you put Platy fry in main tank?

Of course, your fry won’t be fry for too long and at some point they’ll be joining the adults in the main tank.

Count about 4 weeks from the time your Platies were born.  At this stage, the fry are no longer too small to be eaten.

If you think they’re still too small at 4 weeks, consider after about another week.  At this point, they are also able to eat the same food you give your adult fish in the main tank.

How do I stop my Platys from breeding?

If you’re getting overwhelmed with the number of babies and how to care for them, you might just want to put a stop to the reproduction altogether.

There’s no stopping your Platies from breeding as long as they’re together.  As long as they’re mature enough, they will mate.  If you don’t want your Platies breeding you can just keep a couple of males in a 10-gallon aquarium. 

Having females is unpredictable as they may have already been exposed to a male while in the pet store.  If you want to keep an all-female tank, you might want to get the fish while they’re still fry under 4 months of age to ensure no mating will take place.

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