Guppies and mollies are like cousins from the same family, so you may wonder: Can I crossbreed them together?
The answer is yes! You can. But you need to know a few things before you try.
Hybridizing mollies and guppies aren’t without their problems, and there are some surprising things to learn about breeding mollies and guppies together.
Mollies and Guppies Are Close Relatives
Mollies (Poecilia sphenops) and Guppies (Poecilia reticulata) are both members of the livebearing family – and even hail from the same Poecilia genus. That means they’re very closely related and can breed together.
To pair them together still might seem quite surprising. After all, guppies generally only grow to 2 inches in size, compared to the much larger mollies, which can reach 4.5 inches – which means you’ll need to get the pairing the right way around!
What Should We Call the Offspring of Guppies and Mollies?
Some fish keepers have decided that hybrid offspring from a male guppy and a female molly should be called ‘Gollies’ – whereas offspring from a male molly and a female guppy is termed ‘Muppies.’
This all gets a bit silly, though; actually, the names in the fishkeeping community are interchanged quite a lot.
For the purposes of this article, we’ll generally refer to the offspring as Gollies – since you should never pair a male molly with a female molly anyway!
What Do Muppy and Golly Hybrids Look Like?
Hybrid offspring of Mollies and Guppies are rather unpredictable in their appearance, being something of a mix between the two parents.
Don’t expect anything too spectacular, though! I’ve never seen gollies with the same fancy fins or marbled patterns that purebred guppy or molly varieties can have on their own.
In general, this genetic mixing seems to dilute their features back down to something more ordinary or wild looking.
In fact, many golly or muppy fish remind me a little bit of plain-looking platy. They’re somewhere in between the size and shape of guppies and mollies, with less pronounced features!
Potential Problems With Breeding Mollies and Guppies
As we’ve said, the genetic mixing of these two fish often produces less exotic offspring than either of their parents. But there are more serious issues to be aware of if you consider crossing these two livebearers.
Mollies are MUCH larger than guppies – sometimes twice the size. You’re asking for trouble if you try to get a female guppy pregnant by mating her with a male molly.
Remember, these fish don’t lay eggs but give birth to live young! A female guppy giving birth to a large young from a male molly is likely to have difficulties in labor and could even die during the birthing process.
Even if you follow the rules and breed from a female molly and a male guppy, there could still be some problems with the fry. Baby gollies are generally not as strong as either species and are less likely to make it to adulthood than the purebred fry of either species.
Gollies and muppies are also infertile – so you’ll never be able to continue the breeding experiment into further generations.
How To Breed Mollies and Guppies Together
Considering some potential downsides of breeding mollies and guppies together, you’ll need to know if you’d still like to have a go.
Get Your Water Parameters Right
For breeding, your water conditions must be optimized for both parents to be in good condition to breed.
Temperature for these species should be between 70 – 76 Fahrenheit, so you’ll need a heater with a reliable thermostat to ensure this.
Mollies favor harder, more alkaline water conditions than guppies, so you’ll need to set the pH and the GH somewhere between the preferences of the two. A pH of 7.5 and a dGH of 12-18 should meet the needs of both species.
Be sure to keep your water clean with a good filter. Consider giving the tank a good clean before breeding commences, as you don’t want to give your fish further stress once pregnancy has been initiated.
Select the Parents
As always with breeding, you’ll want to choose parents with your favorite features to pass on to their offspring.
A ratio of two male guppies to six female mollies is normally recommended for optimum chances of successful mating.
If there is a mixture of sexes in either guppies or mollies, these fish will usually choose to breed with their own kind!
You need to persuade them to breed with one another by giving them no other options.
Wait for Your Mollies To Become Pregnant
Don’t expect the first mating attempt that you see to mean that your molly is pregnant!
You’ll know when your molly has been successfully fertilized when you see her belly swell up, with a dark spot or line in the center of her abdomen.
You may also notice her feeding more often and becoming more aggressive during pregnancy.
A molly’s gestation period can be between 28-50 days, depending on the type of molly and water conditions, so you’ll have to wait a while for the young to appear.
Move Your Mother Mollies to a Breeding Tank
When you’ve determined that one or more of your mollies is pregnant, you need to move them to a separate tank to prepare for the birthing process.
This breeding tank should be at least 10 gallons in size and contain several plants and a gentle sponge filter.
Ensure the breeding tank is well-cycled and that the water parameters match those of the tank that your mollies came from to avoid any unnecessary shock for the pregnant mollies.
Watch Your Molly Give Birth
In the days before your mother, molly is ready to give birth, she will become increasingly reclusive, spending most of her time hiding among plants or in caves. She’ll swim very slowly and show little interest in food now.
Keep a close eye on her during these days. It can be fascinating to watch her giving birth to live young. She may give birth to anything between 20-100 fry!
Remove Your Mother Mollies From the Tank
Mollies have a shocking reputation for parenting! They normally eat their young in captivity just a few hours after birthing.
You can have some compassion for her. Giving birth to up to 100 fries isn’t easy. She’ll be so exhausted and confused that she may simply snap up the nearest piece of protein that swims by!
If you want any of your fry to survive, you’ll need to remove the mother before she eats most of her young.
Raise the Golly Fry
The tank for the fry to grow up in should have plenty of plants to oxygenate the water and take shelter in. Floating plants, like Amazon Frogbit, are especially good for this.
Raise the golly or muppy fry on young brine shrimp, baby fish food, or quality flake food ground up in a pestle and mortar.
Test the water and perform water changes regularly to keep the tank clean and good for young fish.
Move the Fry to Their Permanent Homes After 1 or 2 Months
After 4-8 weeks, the little fry should be large enough to move to permanent homes. Perhaps some of them can go back into the same tank as your molly/guppy parents.
You’re likely to have more fry than you can keep, so ask your friends or responsible pet stores if they’d like to take some.
A Few Last Questions…
Can I Sell Gollies or Muppies?
As we’ve said, guppy-molly offspring are rarely spectacular to look at. They’re not often sought after and don’t tend to fetch high prices.
If you have particularly interesting-looking offspring, you may be able to sell them to a pet store or even online, but always do this responsibly.
You must ensure that the next owners of these fish know exactly what they’re getting and that gollies are sterile.
Can I Crossbreed Platies With Guppies or Mollies?
No, but they may still try! As you may have noticed, livebearers love to reproduce and may even try to make babies with other fish that look similar.
What Other Fish Will a Guppy Crossbreed With?
Asides from mollies, guppies, can also crossbreed with Endler Guppies, aka. Endler’s Livebearers – a sub-species of guppy from South America.
As with Molly-guppy hybrids, the resulting offspring are often rather weak and fragile compared to their parents.
Some Interesting Alternatives to Gollies and Muppies
If you’re looking to keep some unusual livebearers, there are some other interesting species you could keep that won’t have some of the problems associated with molly-guppy hybrids.
Dusky Millions Fish (Phalloceros caudimaculatus), Humpbacked Limia (Limia nigrofasciata), Cardinal Brachyrhaphis (Brachyrhaphis roseni), and Spotted Skiffia Multipunctata (Skiffia Multipunctata) are all rarer species of livebearers that can offer some novelty to your aquarium.
However, some of these species are rather aggressive and may nip at the fins of other fish.
If you’re looking for a rare, non-aggressive livebearer for the community tank, look no further than the Merry Widow Livebearer (Phallichthys amates) – an active, attractive, yet peaceful fish from South America that none of your friends are likely to have heard of.
Think Twice Before Breeding Mollies and Guppies!
Raising Molly-Guppy hybrids is possible, but the venture has several potential drawbacks.
The fry is unlikely to be as strong, healthy, or attractive as their parents. Furthermore, they will be sterile, meaning their bloodline can’t be extended.
A pregnant molly could give birth to up to 100 babies, so it’s important that you weigh up your options before trying to breed mollies and guppies together.
If you’re looking for interesting livebearers to keep, several wild species out there are just as novel as the elusive golly!