Can Guppies And Mollies Live Together? (Answered!)

Hellboy betta fish
Hellboy betta fish

If there are two fish that would be considered ‘staples’ of the freshwater fish-keeping world, it would be guppies and mollies. Both species of fish are colorful, hardy, and easy to breed. These three traits alone have cemented both guppy’s and mollies’ popularity forever. So you may well ask yourself Can guppies and mollies be kept together in the same aquarium?

Guppies and mollies can both be kept together in the same aquarium. Both species are relatively peaceful. Both guppies and mollies require very similar conditions in the aquarium. Temperature, food, and aquarium setup requirements are all the same making them ideal bedfellows.




Tank Size And Setup For Guppies And Mollies

Ideally, you will want to keep your guppies and mollies together in an aquarium that is 20 gallons or larger. This combination could work in a tank as small as 10 gallons, but male mollies can reach up to 4” (10cm) long, so the larger 20-gallon tank will make life easier.

The aquarium will need to be heated to between 74°F and 80°F (23°C and 26°C). A good quality aquarium heater will be required.

Filtration is important in a tank containing both guppies and mollies. As both species of fish are livebearers the population can quickly grow. I have had great success using a hang-on-back filter in my tanks containing guppies and mollies.

Live plants can also be added to your guppy and molly aquarium. Live plants help keep your aquarium water clean by filtering out some of the fish waste.



Filtering A Guppy And Molly Aquarium

Filtration in your guppy and molly tank is very important. A good quality filter will reduce the amount of harmful ammonia and nitrites in the aquarium water.

Guppies and mollies are both active fish that do need to be well fed. Needless to say, the more you feed, the more waste that is produced. Add to this problem the fact that both guppies and mollies are livebearers and your population can literally explode over just a couple of months.

I have had really good success with the Fluval ‘C’ series of hang-on-back filters. I wrote more about them in this article HERE. Hang-on-back filters are generally quiet and economical to run, easy to maintain, and last for many years.

Feeding Guppies And Mollies Together

Guppies and mollies will both appreciate very similar diets. They are both omnivores and as such a good quality flake or pellet food should be used. I have found Bug Bites by Fluval (read more about Fluval Bug Bites in my article HERE) work really well with both guppies and mollies, as do Vibra Bites by Hikari.

Both guppies and mollies will also appreciate the addition of live or frozen bloodworms, daphnia, or brine shrimp. I try to feed my guppies and mollies live or frozen foods 2 or 3 times a week. Generally, I find frozen foods easier to store than live, so they make up the bulk of my feedings.

I have written an article about what do black mollies eat as well as one which looks at the question Can guppies eat bloodworm?.

Breeding Guppies And Mollies In The Same Aquarium

Guppies and Mollies are both live-bearing species of fish. This means the females give birth to live, free-swimming baby fish.

Guppies and mollies are both species of fish that are essentially pregnant all the time. If you keep one or both of these fish, they will reproduce in your aquarium. Unfortunately, adult mollies will happily eat guppy babies and adult guppies will happily eat molly babies. In reality, they will happily eat their own babies too!

If you are hoping to actively produce more baby fish, a guppy/molly aquarium isn’t the best place as the vast majority of the young fish will be eaten. If instead, you see every baby fish that makes it as a bonus, then you will be pleasantly surprised every time you see a baby has made it.

If you want to increase the chances of babies surviving, there are a few things you can do.

  • Fill your aquarium with live plants
  • Provide lots of hiding places
  • Make sure your filter isn’t sucking babies in

Fill your aquarium with live plants

The benefits of having live plants in an aquarium are almost endless. In this instance, live plants offer two major advantages. Firstly, the algae and microorganisms living on the leaves and stems of your live plants will provide crucial first food for newborn baby guppies and mollies. Secondly, live plants naturally provide tons of tiny hiding places where baby fish can spend their days away from hungry adult fish.

Provide lots of hiding places

As with live plants above, having lots of hiding places reduces the chances of baby fish being eaten. It doesn’t matter to the fish what you use to create the hiding places. A pile of large rocks, a clump of Java Moss, or a Spongebob Pineapple House, is all the same to the baby fish.

When it comes to baby fish not being eaten, out of sight is out of mind!

Make sure your filter isn’t sucking up babies!

Canister filters and hang-on-back filters are notorious for sucking baby fish right into them. Needless to say, once a fish is sucked into the filter, it will be dead.

To prevent the problem, consider adding a sponge to the intake of the filter. Placing a sponge over the intake strainer not only stops the baby fish from getting sucked in, but also stops plant leaves, uneaten food and other debris from getting sucked up, meaning your filter will run more efficiently and the gap between services can be extended.

Can Guppies And Mollies Crossbreed?

Yes, guppies and mollies can crossbreed. The resulting fry are often referred to as Muppies. Muppies are colorful fish that reach 3”-4” in length. Unfortunately, it is widely reported that Muppy fish are sterile and so you can’t then produce future generations of Muppies. You can read more about Muppies in this article I wrote titled Can Guppies and Mollies Crossbreed?

In Conclusion

Keeping guppies and mollies together in the same aquarium is almost always a winning combination. Guppies are super colorful, mollies grow large but remain mostly peaceful. If you set yourself up an aquarium with half a dozen guppies and the same number of mollies, you will not be disappointed!


About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James
Editor