Can Guppy Fish and Molly Fish Live Together?

Many new aquarium owners start small, with just a few fish at a time. It’s a good idea to test the waters first before plunging head-first into this hobby. After all, keeping pets means serious business and a lot of responsibility.

But the magic of the aquarium hobby doesn’t start until you branch out and get colorful and creative. When you’re ready to upgrade to a larger tank and to buy more fish, that’s when things get serious.

But if you’re thinking about diversifying your tank population, you should first consider the type of fish you’re doing to keep. Some species don’t get along due to contrasting personalities, while others have different, contradicting needs. You’ll have to consider their compatibility before enriching your aquarium with different fish species. In this article, we’re going to explore guppies and molly fish. So, if you’re considering this combo, this information should be useful for you.

Can Guppies and Mollies Live in The Same Aquarium?

Well, great news! If you like both of these species, you don’t have to choose. Guppy and Molly Fish can share the same aquarium. Both of these fish are social and peaceful. They won’t typically attack one another, so coexisting isn’t going to be an issue as long as there’s plenty of food. Guppy fish tend to eat just about anything, including smaller fish. The good thing is that Molly Fish are too big to fit into Guppies’ mouths.

You can choose from a wide variety of colorful Guppy and Molly Fish types, and they’re all going to be cool with one another. Their personality traits might vary somewhat according to breed, but both species are usually mellow and friendly. There’s a huge range of colors and patterns for guppies and mollies alike, so there’s something for all tastes.

Sunset Guppies, Koi Guppies, Cobra Guppies, Tuxedo Guppies, and Leopard Guppies are all loved for their beauty and unique appearance. Well-appreciated Molly Fish breeds include the Black Molly, Dalmatian Molly, Golden Lyretail Molly, Gold Latipinna Molly, Balloon molly, as well as the Potbelly Molly.

Water Parameters for Guppies and Mollies

Whatever works for guppies will also work for Molly Fish and vice-versa. So, whichever fish you kept first, rest assured that you don’t need to change your entire tank set-up to accommodate the new guys. Guppy and Molly Fish both do best with brackish water. So, not exactly saline, but not freshwater either. Besides a minimal salt content, both fish species also need hard water.

Because guppies and mollies are both livebearers, they need a water pH of around 7.0 or higher. The optimal pH for Guppy Fish is 6.8-7.6, while Molly Fish thrive in 7.5-8.5 pH water. The recommended water temperature for guppies is 72-82 °F (22-28 °C). Mollies need temperatures ranging from 72-78 °F (22-25.5 °C). As you can see, there’s a lot of overlap between these two species’ needs.

The water must also be clean and free of ammonia and nitrates. When your aquarium population increases, you must also be ready for larger or more frequent water changes. If you haven’t installed a filter yet, now’s a perfect time to do it. Besides good filtration, you should also do at least a weekly water change to keep everything in check.

Food For Guppy and Molly Fish

Both of these fish eat similar diets. They’ll eat just about anything you throw at them, but a good balance of plant and protein-based feed is best. The optimal diet’s a little different depending on your pet’s age. Focus on high-quality, nutrient-dense food sources. Fresh, cooked, frozen, dried, and even live food are all great.

Bloodworms, brine shrimp, daphnia, and even beef heart are all nutrition powerhouses rich in protein and low in fat. That’s exactly what Guppy and Molly Fish need! Spirulina, algae, and green vegetables are full of vitamins, pigments, and antioxidants that will keep your fish vibrant and colorful.

You should feed your adult fish once a day or even every other day. Always be mindful of the portion size. Guppies and mollies are big eaters and they’ll chomp down on every bite of food you give them. Moderation isn’t their thing, so they can easily overstuff themselves. This creates excess waste and can even result in health problems for your fish.

Caring For Guppy and Molly Fry

These fish are big breeders. Female guppies and mollies can get pregnant and give birth to tens of fry every single month. Both fish species also tend to eat their newborns. So, you might want to move your adult fish to a new tank before they start bonding over their cannibalistic tendencies. Keeping your fry in a separate tank completely eliminates the danger of them being eaten alive.

This also allows them to eat and swim around without stress and competition. A separate tank is ideal because feeding your fry might otherwise be difficult. Bigger fish are faster and more agile, so they’ll eat all the food before the little ones can reach it. However, if an extra tank is not an option for you, you can also enrich your aquarium with live plants and other decorations for your fry.

Consider plants such as Hornworts, Guppy grass, Water Sprite, or Java moss to protect your fish. The small fish need hiding spots to retreat to before they grow large enough. The fry will periodically come out of hiding to look for leftover food floating around the bottom of the tank. Once they reach a certain size when they can no longer be eaten, your fry will spend less time hiding and they’ll become more sociable.

Controlling Breeding

Guppies and Mollies have lots of things in common, such as their breeding behaviors. Both female Guppy and Molly fish can give birth to fry every 30 days. On top of that, both fish are livebearers. Female guppies and mollies save the male’s sperm for months after their last encounter. They then use it to get pregnant even in the absence of male fish.

If your female fish have already had an encounter with a male, there’s no guarantee they won’t keep breeding once moved to a separate tank. Male guppies and mollies are both sexually aggressive and they will seek female fish constantly. Even if you only keep one sex of each fish species, the males will still harass the female fish of the opposite species. In fact, their species doesn’t matter at all, because both fish have similar reproductive systems and processes.

This means that hybrid breeding between Guppy and Molly Fish is entirely possible. This is either great news, or terrible news, depending on your goals. If you have enough fish already, there’s only one way to completely avoid breeding more. You have to keep just male fish of each species. As long as there are no female fish in your tank, the males shouldn’t get aggressive with one another.


There you have it! Guppies and Mollies can make great buddies. They have lots in common and very similar water and dietary requirements. You’d only have to make minor adjustments if any, and you’ll be ready to go!

Perhaps the only real change you’ll have to make is to upgrade your aquarium size to fit all your new fish. Otherwise, you can continue to look after your fish just as you would before. There’s also the added bonus of hybrid breeding these species if you’re interested in that.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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