Guppy Fish and Molly Fish – Can You Keep Them in Same Aquarium?


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Many people prefer peaceful fish for their aquarium. Also, most opt for fish that are similar in nature and can easily coexist with each other. In this article, you will find out whether guppy fish and molly fish can live together in the same fish tank or not.

Mollies and guppies are very similar in nature. Both are peaceful fish and they are live-bearers. This means, that they will not lay eggs, but will give birth to live fry.

Keeping Guppy Fish and Molly Fish in Same Tank

So, can you keep guppies and mollies in the same tank? The answer is YES, you can keep guppy and molly fish in the same aquarium.

Below you will find some interesting things you should know about before putting guppy and molly fish together in the same tank.

Guppy and Molly Fish Types

There are many types of guppy fish and molly fish which you can choose from.

The exact behavioral traits of the fishes can vary dependent on the breed which you choose. In general, most of the breeds of guppies and mollies are compatible with each other since they are peaceful.

Guppies are categorized by colors, fin types, patterns, name of breeders and more. Here are some of the most common guppy types:

  • Moscow guppies
  • Sunset guppies
  • Cobra guppies
  • Tuxedo guppies
  • Snakeskin guppies
  • Mosaic guppies
  • Leopard guppies
  • Grass guppies
  • Lace guppies
  • Koi guppies
  • Red eye guppies

The molly (Poeciliidae) family has also various types. These are the most common molly fish types:

  • Black molly
  • Gold latipinna molly
  • Golden lyretail molly
  • Potbelly molly
  • Dalmation molly
  • Green sailfin molly
  • Ballon molly

Feeding Guppies and Mollies

The good news about feeding is that both guppies and mollies will eat the same type of food. Their main food should be vegetable-based, but they will basically eat anything you give them.

You can offer them live food, cocked vegetables, frozen food such as blood worms, freeze-dried food, veggie pallets, spirulina or even beef heart. Check out my magic recipe for guppies which are also great for feeding mollies.

There is no need to feed your fish very often. This will only pollute the water and will cause problems. Feeding your guppies and mollies once a day or every other day is more than enough. Avoid overfeeding at all cost.

Most fish keepers think that their fish are hungry. The fish gather to the front of the aquarium once you approach them. Fish are always hungry! But keep in mind, that just like in humans, too much food can cause health issues.

Guppies as well mollies like to nibble on algae. Mollies however are bigger algae eaters than guppies. So if you have an algae problem in your tank, mollies will take care of it. Mollies will not consume all types of algae, but they will eat any softer algae.

Guppy and Molly Fry Care

Guppies as well mollies give birth to live fry every 30 days. Unfortunately both species eat their fry, so it is pretty difficult to protect the guppy and molly babies in their parent’s aquarium.

If you want to save and raise the guppy and molly fry, you can either raise them in a breeding box (though I don’t endorse this technique) or you can use a separate tank for this purpose.

You can either scoop out the female guppy of molly from the main tank and place it in a separate aquarium until she drops the fry; or you can scoop out the fry from the main tank. The second option is a lot harder.

If you don’t have the option to put the fry in separate tanks, you can add lots of live plants to your aquarium. The plants will provide enough cover for the fry to hide from the parents and do not get eaten. Fry will feed on algae, biofilm and small junks of leftover food which is floating through the water column. They will hide until reaching a certain size.

Here are some easy plants that you can use to protect guppy and molly fry:

  • Java moss
  • Guppy grass
  • Hornworts
  • Elodea
  • Watersprite
  • Amazon frogbit

Keeping Right Water Parameters

The natural habitat of guppies and mollies is brackish water. The salt content should be minimal. However, they can live and breed in fresh water as well. If you want to mimic the natural water conditions, it is a good idea to opt for brackish water tank.

Since they thrive on similar water conditions, you will not have to worry about achieving any balance. You have to just make sure that the water is slightly salty and you will be able to create the perfect habitat for them. Both fish like hard water, so take this in consideration too.

Frequent Water Changes

Guppies and mollies can breed pretty fast. More fish results in an extra amount of waste in your aquarium. While with the help of a filtration system, you can eliminate some of the waste but it is important to keep the proportion of nitrates under certain levels. This can be done by changing the water frequently.

You have to create proper water changing schedule and you have to stick to it. A weekly 30-50% of water change should be enough for most aquariums. However, for overstocked fish tanks you need to monitor the ammonia levels and make more frequent water changes.

Population Control

As mentioned above, both guppy and molly fish are live-bearers. The females in both of these species save the sperm even after a single encounter. The molly fish can use this sperm for up to 3 months to get pregnant multiple times.

The guppies, on the other hand, can use the sperm for a lifetime and get pregnant again and again. This means that even if you introduce only the female sex of each species into your aquarium, there are chances that they might get pregnant from the previous encounters. Thus, it can become difficult to control the population over a longer period of time.

Another problem which you might face is that if you introduce only one sex of each species into the aquarium, they can reproduce with each other. This is specifically true when they do not have access to the opposite sex in their own species.

Thus, hybrid breeding is possible between mollies and guppies. This makes population control even difficult. If you can’t have complete control over the population, you have to introduce only males or females only of both species into your aquarium.


If you want to keep guppies and mollies together, just go ahead and do not worry about too many things. Maybe this article was a little too scientific, but I hope you learned something from it.

Updated: November 18, 2021
Questions & Answers
  1. Can I put , gold fish, cuppies, mollies, koi fish all together in same tank, my tank size 2.5 feet…

    1. avatar

      I don’t think koi fish would go with guppies or mollies. I don’t recommend this combination.

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